PROCEEDINGS

Vol. _XII, pp. 41-51

March

24, 1898

PROCEEDINGS

OFTHE

BIOLOGICAL SOCIETY OF WASHINGTON

THE ARCTURIDjE IN THE U.S. NATIONAL MUSEUM*

BY JAMES

E.

BENEDICT,

Assistant Curator, Division of Marine Invertebrates, U. S.National Museum.

When Mr. Beddard wrote

the

Report on

the

Isopoda

^collected

by

^the

'Challenger'

ⁱⁿ 18S6,

hut

five species of Arcturus

had been

recognized.

He added

thirteen.

Since

his report

no

addi- tional species

have been

described.

In

this

paper

^five species

taken by

the 'Albatross^'

and one by ^{the Point} Barrow Expedi-

tion aredescribed as

new and

a subspecies ^is raised to specific rank.

The

structure

and

habits ofthe Arcturida) are

such

that

deep- water

_species are _likely to

occupy only

^{restricted areas.}

The young

^are

^few

^{in a}

^{brood and}

^{arecared for}

by

^the

parent

^until well abletocareforthemselves, clinging^tothe

mother's antenna?

until

ready

^to

undertake

a

more independent

existence,

perhaps on

the

very

object

on which

the

mother

is foraging ^for herself

and

^brood.

With

habits ofthis

kind

the

chances

of a

wide

dis- tribution for

any ^one

species

must

lie

very much

less

than

is the case

where free-swimming young

^arc

produced

ⁱⁿlarge

numbers.

The

character of the

marsupium

^{of Arcturus is sufficient to}

separate^this

genus from

Astacilla.

The

_{dactyls of}

some

_species

of Arcturus are

biungulate

^{as in Astacilla.}

Two

species of ^Astacilla are described as

new, one from the

Straitsof

Magellan and

a blind species

from deep ^water

(1,825

fathoms

oil'

Martha's Vineyard. The

finding of a blind ^Astacilla in

deep water

^{is a}

matter

of

no

^little interest.

Mr. Beddard

*Published

by

permissionof the Secretary of theSmithsonian Institu- tion.

10—Biol Soc. Wash., ^Vol.. XII, 1898 (41)

42 Benedict —

_Arcturidse

_in

_{the U. S.}

_{National Museum.}

trulysays of deep-sea

Isopoda

^:

*

"Although

^the

number

of

deep-

sea species

which have well-developed

eyes ^is so _large,

they nearly

^{all (all}

except

three)

belong

^{to the}

two

allied

genera

^Arc- turus

and

_Astacilla,

which thus form almost

the

only exception

to the general

statement

that deep-sea

Isopoda

^are blind."

Of

Astacilla

he _says

:f

"

Unlike

_Arcturus, Astacillais

almost

exclu- sively

an inhabitant

of the

shallow

_waters,

only one

species, in- deed, ^Astacilla granulata,

ranging

^into

deep

water."

Key

to tfie Species of Arcturus.

a.

End

of the

abdomen

_notched,asseenfromabove.

b.

Body smooth and

^freefromspines ^. beringanus.

1/.

Body

spiny.

c. Plead

and

six segments^of the thorax each witha

pair ofspinesonthe

dorsum

longispinis.

c^/.

Head and

_segmentsof the thorax with not less

than

two

_{pairsof spines}to thesegment.

d. Second

and

thirdarticlesoftheantennae with-

out spinesexcept^atthearticulations _hystrix- cY. Second

and

thirdarticlesof theantennaewith

spinesonthe bodies of the^articles murdochi.

a'.

End

ofthe

abdomen

withoutnotch.

b.

Thorax

withoutspinesabovethe epimera.

c.

Abdomen

acute or subacuteatextremity.

d.

Eyes

^elevatedonpeduncles ^oculatus.

(V. Eyes not^elevated on_peduncles.

e. Extremity^of

abdomen

notched ina lat- eral view.

f.

Thorax

very tubercular stebbingi.

P.

Thorax

not tubercular abyssicola.

e'. Extremity^of

abdomen

without notch,

f. Fourth segment of the thorax

much

longerthanthe precedingsegments^. glabrus.

f. Fourth segment^{of the}thoraxbutlittle longerthanthe preceding segments, g.

Thorax

with _{large swellings} or

tubercles tuberosus.

g'.

Thorax

withouttubercles myops.

c'.

Abdomen

roundedatextremity.

d.

Abdomen

notched atitsextremity^{in lateral}

view spinifrons.

d^/.

Abdomen

without notchatitsextremity.

e. Epimeralspinespresent anna.

e'. Epimeral spineswanting coppingeri.

*Report

on

theIsopoda^collected

by

the 'Challenger,' ^p. !(><>.

fOp. tit., p. 107.

Arcturidse in the U. S.

National Museum. 43 Thorax

with _spinesabovethe epimera.

c. Spines present ⁱⁿ frontofthe ocular_space.

d. Spines, spinules, or spiny tubercles very nu- merous on the thorax.

e. Spines^all long

and

slender multispinis.

e'. Spines^allshort orwith a few_{long ones,}

f. All spinesshort.

g. Third segmentof antennae spinu-

lose furcatus.

g'. Third segmentnot spinulose.^... glacialis.

i'. Spineslong

and

short.

g.

With

three spinesextending back

fromthe

abdomen

_spinosns.

g'.

With

two _spinesextending back

fromthe

abdomen

americanus.

d

^/. Spines of thethorax comparatively^few.

e. Lastsegment^ofthe

abdomen

withacate- nate

median

line,

f. Second segment ^of

abdomen

with

spines cornutus.

f'. Second segment withoutspines tenuispinis.

e'. Lastsegment without^carina.

f.

Abdomen armed

with_{a long}

median

spine

which

_projects

beyond

^the

end

ofthesegment.

g.

Upper

^surfaceof

abdomen smooth

.purpureus.

g'.

Upper

surface spinulose studeri.

F.

Abdomen

without

median

_spine brunneus.

c'. Spinesabsentin frontof the ocular_space.

d.

Head

freefrom_{spines feiideni.}

d^/.

Head

with_{spinespresent}be;

ween

_{the eyes.}^. _baffini.

Arcturus

baffini(Sabine).

Idothea _baffini Sabine,

Appendix

^to Parry's ^First Voyage, p. 50, pi. i, figs. 4-6, 1824.

Arcturustuberculatus Latreille inCuvier,

Regne

Animal, ^ed. 2,IV, p. 139, 1829.

Arcturus_baffini

Westwood,

^Trans.

Entom.

Soc.Lond., ^vol. I, p. 72, 1836.

Milne-Edwards, ^{Hist. Nat.} Crust., Ill, p. 123, pi. xxxi,fig. 1,1840.

Sars, Crust. Norw. North Atlantic Expd., p. 97,pi. ix,figs. 1-21, 1885.

Beddard, Report

on

theIsopoda^collected by^the

'

Challenger,'pi.

xx, fig. 12, 1886.

The

best _figuresofthis species are, in

my

opinion, those of Professor Sars. Itisthe oldest

and

best

known

_speciesof the genus,

and

liasbeen taken over a _larger range than

any

^{other. Its characters are so well}

marked

that itcan be _{readilyseparated} from

any

^other species inthe collection.

44 Benedict— Arcturida

in the U. S.

National Museum.

Arcturus

feildeni Miers.

Arcturus

baffinivar. feildeniMiers, Ann.

and

Mag. Nat. Hist, (4)

XX

⁶⁴

1S77.

The

headisalittlebroader than_long

when

_{the length} ismeasured on theside; the surface presents threeareolations,twocircularonesalittle infrontof thelineof the eyes

and

a long transverseone behindthe_eyes.

The

antenna? are equal^tothe

body

ⁱⁿ

length—

³⁶

mm.

; the fourth

and

fifthjointsareeach 11

mm.

The

four anteriorsegments^ofthethoraxare without spines or tubercles;

two

_slight areo- lations nearthe anteriorborderof thesecond

and

third segments donot correspond ^{to the} spines ofbaffini, as they^exist on that _species in additiontothe_spines.

The

^fourth_segment

is equal ⁱⁿlength^to the

two

_preceding.

The

three posteriorsegments^ofthethorax

and

the twoanteriorsegments^{of the}

abdomen

areeach provided^{with a}pairofsmall blunt_spines.

The

middlesurfaceof the

abdomen

is with- out

any

^{indicationof the}prominentspiny pro- jectionsof_baffini; the

median

line,ontheother hand,

shows when

^{dried a}slight irregular

me-

dian groove.

The

conicallateralprojections of baffini are altogetherwanting ^{in this} species.

The

_epimeraarealso

much

modifiedin feildeni;

they^are

much

less pointed,

and

are directed

downwards, making them

inconspicuousfrom a dorsal view.

The

surfaceof the

body

^isgla- brous.

The

above description ^is based on a single specimen ^labeled

'Camp

^Clay,

Cape

Sabine; Lieut,

[now

General] ^A.

W.

Greelv.'

(No._{12416, U.}S.X.M.)

A much

_larger

and

less typicalspecimen ^islabeled

'Arcturus_baffinivar.

tuberosus, DavisStraits.' Thisisidenticalwith the

Cape

^Sabine specimen, except that the spines of the posteriorseg- mentsarereducedtovery low tubercles.

The

_{range of} variation, as^in- dicated bythe

two

_specimens, ^is easilywithinspecific limits; bothare far

removed

from A. _baffini. Length ^of specimen from^{the fronttothe}

abdomen

50

mm.

(No. 20333, U. ^S. N. M.).

Fig.:;. -Arcturusfeildtm

(X%)'

Arcturus

longispinis sp. nov.

This_species, though ^well marked, partakes strongly of the characters of baffini, the type of the genus.

The

headisdeeply concave ⁱⁿ front; the margin does notforma true curve, but

shows

_slight projections between the

median

and outer an- tenna.'.

The

eyes are triangular

and

conspicuously protruding.

The

Arcturichi in tin V. S.

National Museum. 45

basal _jointsofthe

median

antenna? areoblong

and

flattened; the outer antennaeare52

mm.

in length; the firsttwojoints are but little longer than_broad, whilethe threedistal joints are long; ^all are

unarmed;

^the

flagellum ^is

composed

^{ofabout 12short} segments.

The

spines of the head and dorsal region are placed ^like those of baffini^; with the exception of thoseonthe posterior portion of the thorax, they^are

much

longerthan in

any

specimen^ofbaffini that I haveseen;

the spines of theheadare6.5

mm.

ⁱⁿlength, while those of thesecond, third, andfourthsegments ^are hut little shorter.

The

_spines on these segments^{are united at the base} by^a low_ridge

which

curves up onthe spines,giving

them

the appearance of parts of asingle structure. Be- tween the anterior spines

and

the epimeral projections ontheirrespective segments ^are low protuberances^; ridges ^also

run from the bases of the spines along the margins^tothe posterior angle of thesegments, leaving a deep ^transverse groove below ^the spine.

The

spines of the ^first thoracic _seg-

ment

are very^small

and

inconspicuous^{; it is} possiblethatthissegment

may

^notbe

^normal

in regard^tothe_{spines, as}it is partially over-

grown

by^acolony of Polyzoa.

The

_epimeraof the second,third,

and

fourth segments^{increasein size}posteriorly^; they^are flattened

on

the exposed ^surface

and

_evenly rounded below; thereis a depression on the exposed^face.

Viewed

from_{above, the}epim- eralprojections arecovered by large

rounded

tubercles

on

the lower margins ^of the _seg.

ments.

The

_epimeraof the fifth, sixth,

and

seventh segmentsdecrease in size posteriorly,

and

are broad

and

wedge-shaped^; the spines of thesesegments^arethe

same

in characteras those of the anterior segments, but are

much

smaller, measuring on ^{the fiftli :!}

mm.,

the sixth2.3

mm.,

^{seventh2 nun.}

The

first abdominal segment ^isvery short, with twosmall spines above

and two

conical projections below; the second segment has

two

_longspines above, pointedbackward,

and none

below; the terminal segment has two

spines pointing

backward

insertedat aboutthemiddleof the dorsal sur- face;at thispoint thesegment^israpidlydepressed^totheterminal_points;

the lower margin has

two

_pairs of triangular projections; A. _baffinihas but one_pair.

Station _3599, latitude 52° 05'

00"

_N., longitude 177° ^40'

00"

_W., 55 fathoms.

Type

(No. 20530, U. S. X. _M.)'-

Fig. 4.--Arcturuslongispinis.

(Xltf.)

46 Benedict — _Arcturida

_{in the U. S.}

_{National Museum.}

Arcturus

glabrus_gp. nov.

The

head is widerthan _long, measured inthe constriction in frontof the eyes

and

on the

median

line, but longerthan wideif thesideof the headistaken.

The

antenna- are longerthan the

body

^{in both sexes;}

much

_longerin thefemale than inthe male.

There are no spines or tubercles onthe heador posterior ^toit.

The

segments^{of the}thorax

and abdomen

are

smooth

totheeye

and

arefinely reticulatedunderalens.

The

fourth segment ^{differs in} the sexes; ⁱⁿthe male it is a little longer

and more

slenderthan the

two

_preceding segments taken together; ⁱⁿ thefemale itis shorter

and

stouter; sodifferent is the appearance ^thatthe sexes can be _readily separatedⁱⁿadorsalview.

The

anteriormargins of the second, third,

and

fourth segments ^are notched

on

the

median

line.

The abdomen

is

composed

^oftwosegments, an- chylosed, the usual secondsegment being only^in- dicated

by

a swellingabove

and

a short sutureat theside. Thereare nolateralprojections on the

abdomen

; theepimeraof the posterior part of the thorax cannot beseen from above.

The

_dactyls ofthe_posterior feetare biungulate.

The

_length ofthe

body

^{of amale is31}

mm.

; of theantenna?

38

mm.

; female,

body

²⁸

mm.

; antennae45

mm.

;

female,

body

²⁴

mm.

; antenna'^.".'.)

mm.

A number

of specimens ^{of this} species were taken bythe 'Albatross'atStation_{3599, in}Bering

Pig.b.-Areturus_glabrus, f.

Sea,^lat.N. 52°05',long.

W.

L77°40',in 55fathoms (No. 20529 U.S.N. _M.).

(xiMO

Arcturus beiinganus

sp. nov.

The

headisexcavated ⁱⁿ front; thelateral projections arebroad; deep constrictionsor depressions existboth infront and behindthe_eyes.

The

antenna'

when

laidoff

on

the

body

reach the base of the

abdomen

; the fourth

and

fiftharticlesare very long; the flagellum^is

composed

^ofseven or eightarticles; the anten-

nulsereachtothe

end

of the secondarticleof the antennae.

The

first

and

lastthree_seg- mentsof the thorax are near- lyequalⁱⁿlength ;the fourth segment ^isa little

more

than ^Fu twice as long^as any ^{of the others.}

mentsare concave

on

eachside ofthe

median

line tothe posterior angle ofthe segments,

making

^a

more

or lessacute point^at the middleof the segment

and

lobate posteriorangles.

;.<;.

—

Arcturus beringanus. ⁽ %%)

The

_{posterior margins} of the_seg-

Arduridse

in the U. S.

National Museum. 47 The abdomen

iselongated

and

slender; thefirst

and

second segments arc clearly defined ; athird isindicated

by

^adeep

and

irregular constric- tion; theterminusisincised.

A

_large

number

ofspecimens

show

a_light linerunning along theme- dian lineof the dorsal surfaceand _{along the}sides in line withthe_eyes.

The

dark coloredor shaded portions of the surface are

made _up

of nu-

merous

black_spots.

Now

and then_{a large}female isveiy light in color, thelinesbeing butslightly indicated.

The

_{largestspecimens}areIS

mm.

_{in length.}

Station _3252,lat. 57° 22'

20"

_{N., long.} 164° 24^/ 40/' \V. ; depth ^L'it.l fathoms; specimens very numerous. (Type, No. 20529, U. S. N. M.) Station_3253,lat.57°05^/

50" N,

long. 164° 27^/15"

W.

; depth³⁶fathoms;

four specimens. Station_3637,lat,57° 06'

30"

_{N., long.}170°28'

00" W.

;

depth 32 fathoms; one ^female with a_single

young

clinging ^to thean- tennae.

Arcturus

tenuispinis sp.

now

This_species isvery close to A. cm- untax Beddard.

The

head isdeeply excavated infront; a pair ofspines^{arise infront}ofthe interocular space

and

extendforward, diverging a ^little

more

than those ^<>f A. cornutus.

The

firstsegment^ofthe antennaeextendsbe-

yond

^thelateralprojections of the head not

more

than0.2of a

mm.

; thesecond joint measures about 1.4

mm.

on the upper surface, the third _{joint 5}

mm., and

the fourth 13

mm.

in length^; the fifthjoint^islostor brokeninboth_spec- imens.

The

antennulse reach themid- dleof the thirdsegmentof the antennae.

The

first

and

second thoracicsegments are both

armed

with epimeral spines

and

_{a pair} farther back

and

_{higher up} onthe segment; ^theother segments^of thethorax have epimeral spinesonly^; thefirstsegment^{of the}

abdomen

hasa pair of spines^{in line} with theepimeral spines of the thorax; ^{the second} seg-

ment

is altogether

unarmed;

^{the last} segment^has

two

paired spines

and

one unpaired^{; the latterisat the}terminus of a dorsal carina which can only ^he

made

outwith difficulty.

The

_largest spines onthe

body

^arethe pair ^atthe sides

on

theproximal

end

;the spinesat

thedistal

end

areslender; the terminal outline of thesegment^isrounded.

A. tenuispinis can be distinguished from cornutusby ^the

more

slender spines,

by

the lack ofthe extra paironthe third

and

fourth segments^of the thorax, the

unarmed

second segment ofthe

abdomen,

the lack of

Fig.7.

—

Arcturustenuispinis. (X2.)

48 Benedict — Arduridse in

the U. S.

National Museum.

spinesonthe_jointsoftheanteriorseriesof ambulatorylegs,

and by

^the outline of the

abdomen.

_Length ^ofthelargestspecimen²³

mm.

Station _2756, off

Cape

^St. Roque, Brazil, ^hit. 3° 22'

00"

S., long. 37°

49'

00"

W., ⁴¹⁷fathoms;

two

males _(No. 21252, U. S. N. M.).

Aicturus americanus

Beddard.

Arcturus americanus Beddard, Report on ^the Isopoda ^collected by ^the 'Challenger,'p. 104,pi. xxiii, tigs. 5-8, L886.

Color of specimens ^inalcohol:

Body

light straw _color; the head is

shadedwith purple; thisshadecontinuesintwo brokenlines tothe sixth segment, where ^{the lines} are united, spreading again on the

abdomen.

Another brokenline runsalong the second, third,

and

fourthsegments atalittledistanceabovetheepimera^; onthe posteriorsegments^theline

iscontinued close to the epimera. There are

two

purple rings

on

the third _jointof the antennas

and

abroad hand near thedistal endsof the fourth

and

fifthjoints.

Specimens were obtained^attwostationsofftheeastcoast ofPatagonia^: Station _2768, lat, 42° 24^/

00"

S., long. 61° 38'

30"

W., ⁴³ fathoms;

Station _2770,lat. 48° 37'

00"

S., long. 65° 41/

00"

W., ⁵⁸ fathoms; four specimens.

Aicturus

multispinis sp. nov.

The

headisalittleelongated^; thefrontisconcave.

The

_{eyes are}round

and

stand outfromthe sidesof the headas hemispheres.

Two

spines are placed near the frontⁱⁿadvance of the lineof the eyes

and

atrans- verse lineof six alittlebehind the eyes^; the terminal spines of the

row

are

much

smallerthantheothers.

The

antennae are 2S

mm.

inlength

and

slender in comparison with those of the Arcticforms; there are two _spines on the second segment

and two

onthe thirdsegmentof one, and threeon the other; the fourth segment^is

armed

with_{.asinglespine} atitsarticulationwiththe fifthseg-

ment

; the fifth segment ^{is consid-} erably longer than the fourth; the flagellum^isshort

and

withoutjoints.

The

twospines near the frontform the anterior ends of

two

rows that extend to the ^last segment ^{of the}

abdomen;

the first four segments of thethorax havea transverse con- striction

making them

ⁱⁿappearance double segments^; both the anterior

Fig.8.—Arcturusmultispinis. (X2%.)

and

posterior portions of theseseg-

ments

furnish a_pairof spines^forthelateral dorsal linesof spines^{; after}

Aretnrithi in flic U. S.

National Museum. 49

the fourth segment^thereisbuta_{single pair to}asegment^{; thelinesare} not continuedonthelastsegment, but^arehere replaced

by

^{a rowof five} spinesonthe

median

lineofthiselongated segment.

Tin-second segment^{of the}thoraxissoldered tothe head as inother species, otherwise ^itsdorsal armatureis like thatof the three following segments.

The

_epimera of thefouranteriorsegments^of the thorax are moderately extended

and

bear from two to four spines; between the epimera and^thelateraldorsal linesaretwo_spines; thereisanother_spine just behindthe epimera.

The

three posterior thoracicsegments^are

much

shorter

and

narrower than the preceding segments; ^theepimera ^{bear but a} singlespine; the spines of the ^lateral dorsal lines aresmaller than the anterior spines of theline; on thefifth segment, between ^{the line}

and

the epimera, are three spines; on the sixth two _spines, onthe seventh one_spine.

The

Hist two segments^{of the}

abdomen

are dorsally ^like the last segment ^of thethorax; thelastsegment^iselongated

and

bears \\\erows_{of spines}

—

one on the

median

line

and

two on eachside; thereisa longitudinal

row

of livespines on eachvalveof the operculum. Length ^of

body

^23nun.

Station _{2807, off} the Galapagos Islands, ^lat, 0° 24'

00"

S., long. 89°

06'

00"

W.,812 fathoms.

One

female with eggs (No. 21253,

V

^.S. X. M.).

Arctuius murdochi

_sp. nov.

Arctunis_hystrix HargerⁱⁿMurdoch, Report Expedition^{to Point}Barrow, Alaska, p. 142, 1885.

This_species isclosely related to A.hystrix, Sars,fromoffHelgoland

and

Lofoten,from depthsrangingfrom 350to457 fathoms.

Both

_specimensof-4.murdochi

came

from_13^ fathoms 10mileswestof Point Franklin, Alaska, ^collected by the Point

Barrow

Expedition.

The

headisdeeplyconcaveinfront; thesides ofthe head extend forward in frontof the eyes and end in bifurcate projections.

On

the front margin ^{of the} headis a_{single spine,}conspicuous ⁱⁿbeing theonly spineoccupying^the

median

linethroughoutthe length of the animal. A _spine on each side of the

median

spine divides the space between the _eyes,

making

^a row ofthree spinesonthe front of the head_justin ad- vance of the anterior line of the _eyes.

The median

spine ^isa little in advance of the other two. A row of_eightspinesoccupies the posterior part of thehead;

fourof

them

are higher

up

^{than the} eyes

—

_onepair

behind _{the eyes}

and

onebelow on the margin^{of the} head; the spinesbehind the eyes are the^smallest.

The

antennuhe are very short and small, hardly reaching the antepenultimate joints ofthe _largean- fig

tenure; the basal joints are wider and shorter than those

shown

_byProfessor Sars in his figuresof_hystrix.

The

basal jointsoftheantennae are smallandareconcealed fromadorsal view by^{the lateral} projections of the head.

11—Biol.Soc. Wash., Vol.XII, 1898

9.

—

.1returns,nur- dochi.

(X3%.)

50 Benedict —

Arcturidtc in the U. S.

National Museum.

The

second_joint isaboutasbroadaslong

and

is

armed

withthreeshort spines; the third _jointis

armed

with

two

spines pointing outward

and upward;

^{the fourthand fifth} jointsare long

and

slender,

unarmed;

the flagellum has but three joints.

The

first thoracicsegment,^{as in} hystrix, liasa transverse rowof eight spines; the thin ^sidesof thesegment ^ex- tend forward underthehead; thesecond and third segments^also have eight spinesarranged^{as inthefirst.}

The

fourthsegment^issoconstricted in themiddleas togive^itthe appearance ^oftwo segments anchylosed^; thissegment ^hasadoublerow of eight spines^; between thetwo

median

spines of the posterior

row and

theconstrictionaretwoadditional spines;

these spines are smaller than those of the

median

rows,taking ^{the ar-} rangement longitudinally.

The

_{fifth, sixth,}and seventh segments have spines regularly placed on each side of the

median

line; next farther

down

onthesegment ^are

two

spines longitudinally placed; next, on the margin,are three spines united^atthe_base,themiddle onelargest.

The

firstabdominal segment^isveryshort,withatransverse

row

ofsixspines;

onthesecond segmentspines are placed on the two

median

linesonly^; these aredoubled and crowded.

On

theterminal segment^{there are}two rowsof small spines regularly placed on one specimen

and

disarranged

on

theother.

The abdomen

isterminated by twoblunt divergentspines.

The

_specimensare sparsely ^set with_short, stiff hair. All of the_legsare

armed

witha_singlespineonthe basaljoint.

This_speciescan readily be distinguished from _hystrix by ^the

median

spine of the head,by ^{the extra} pair of spines on the fourth segment^of the thorax,

by

^thearmatureof the antennae,

and

_bythe arrangement^of the spinesonthe

abdomen.

As

Professor Sars _{suggests, hystrix}

may

^be

made

the type of a

new

genus; ^itwill then be necessary ^toplace^this specieswith it. (No. 7915,

U. S. N. M.)

Astacilla granulata (G. 0. Sars).

Leachia granulata G. O. Sars, Arch. Math. Nat.. II, p. 351, 1S77.

Astacilla <<iitn-ic<tn<i Harger,

Am.

Journ. Sei., (.'J)

XV,

p. 374, 1878.

Astacillagranulata Harger, ^{Proc. IT. S.} Nat, Mus., II, p. 161, 1N7!>.

Astacilla granulata Sars, Nor. N. Atlan. Expd., Crust., p. ^1(17, pi. ix. ^{fi^s.}

27-35, 1885.

One

specimen fromthe Gloucester fishermen,

Grand

Banks.

Astacilla

diomedeae

_sp. nov.

The

headisexcavated _{in front,} nearly rectangular, a^littlebroaderbe- hind than in front,

The

_{eyes are} butlittle swollen, are round, andare situated alittle anteriortothemiddleofthe margin.

The

antennas areclosely likethose ofAstacilla nodosa (Dana).

The

firstsegment^of the thorax has the

same

width asthe head ; the second

and

third segmentsare successivelywider

and

alsoshorterthan the first; the fourth segment ^is very wide at the anterior end, as in nodosa; likethelatter,^ittapers gradually

backward

tothe fifthsegment.

The

_{segmentsposterior}to the fourth are longerthan the firstthree

and

are successivelv narrower.

Arduridse

in the U. S.

National Museum. 51

Fig.LO.—Astacilla diomi^'I'a. ( 0.i

The abdomen

isconstrictedatthebase

and

liassub- parallel sides^; fromthe_slightpostero ^lateralprotuber- ance itnarrows _rapidly tothe apex.

The

animal isthroughout

smooth and

_glabrous; the

median

line is light in color: on the fourth segment thelight colorbroadensout

and

thesidesareblotched with dark shadings

made _up

of small black spots^{; all} the^articlesof the antenna] peduncles have^a narrow ring of black ^at thedistal ends,except^{the fifth.}

Described from_{a single} female dredged by ^{the 'Al-} batross^' in theStraitsofMagellan from ^adepth ^{of 17} fathoms (Station 2774).

The marsupium

^isfilledwith eggs (No. 21251,U. S. N. M.).

Astacilla caeca _sp. nov.

The

headis deeply excavated ^{to receive the anten-} nulse; theexcavationisdeeper^atthesidesthan onthe

median

line: a rostriform point extends betweenthe antennulse.

The

lateralprolongations of thehead have two _{paired digital processes} nearthe lower margin;

one_pair oidy can ^{be seen}fromabove.

The

antennae reach hack to the

end

of the sixth segment.

As

in other _{species of} the genus, the ^first thoracicsegment

issolidlyunitedtothe head

; thelower marginsof^the segmentare tubercular.

The

secondthoracicsegment

isshort and narrow; ^{the third is}a little longer

and

wider; the fourth or longsegment^is yetwideratthe anterior end,caused

by

the swellings^atthe insertions of the_legs; after this ittapers gradually^to nearthe posterior end,where the taper ^is

more

_rapid.

The

fifth, sixth,

and

seventh segments ^are successively narrower.

The median

lineof the head

and

thorax

istubercular; theheadhasonetuberclenearthe front and another onthe postcephalic lobe; allthoracic_seg- ments have a tubercleon the _line; the lateral mar- gins of^allare angular^; abovethe epimeral projections of thefifth segment are four paired ^tubercles.

The

first segment^{of the}

abdomen

is narrow

and

formsa

neckbetween thethorax andthe broad

and

angular terminal segment.

The

terminal segment^{has a pair}of angular projectionson each sideof themargin^; betweenthe angles themargin^isbutlittlearcuate; posterior tothelastangularprojection the outline^isthat ofanequilateral triangle.

Attached tothe carapace are ^several specimens^of Foraminifera which Dr. Flinttells

me

_belongtothegenus Truncatulina.

Both specimens have beenrepeatedly

examined

foratraceof eyes with- outsuccess.

Lengthof the_largespecimen (female)^H nun.,measured fromthefront.

Station 2714, ^lat. 38° 22'

00"

N., long. 70° 17'

30"

_W., 1825 fathoms (No. 12026, U.S.N. _M.).

Fig.LI.—Astacilla caeca. (X3.)