BIOLOGICAL SOCIETY OF WASHINGTON^

73

Vol. 36, pp.147-156

May

^{1, 1923}

PROCEEDINGS

OF THE

BIOLOGICAL SOCIETY OF WASHINGTON^

* ^FEB _{25 1936} t

NEW MARINE TANAID AND ISOPOD CRUS^^D^A ~

i

e O^

FROM CALIFORNIA.

BY PEARL LEE BOONE.

The numerous contributions

of

Tanaid and Isopod Crustacea from the west

coast of

North America received

at

the United

States

National Museum

^since

the publication

of

Dr. Harriet Richardson's masterly "Monograph on ^the Isopods

of

North America, " have

necessitated

an

additional

report on

this

fauna.

Delays

in

the publication

of this

work make

it desirable to give status

now

to

the new forms found. The one new genus and new

species of

Tanaid and the two new genera and

five

new

species of

marine Isopods

herein

described

will

be more

fully discussed

and

illustrated in

a forthcoming monograph.

Order:

TANAIDACEA.

Family: Apseudidae.

Genus: Dalapseudes, new.

Second antennae without scale.

Exopods

present on both pair of gnathopods. Epipodytespresent on last fivepairs of legs. Three pairs ofpleopodaare present,thebranches ofwhichare welldeveloped.

Eyes

present.

Abdomen

consists of six distinct segments. Mouthparts well developed. Unique.

Type: Dalapseudes pedispinis,

new

species, from

Laguna

Beach, California.

Dalapseudespedispinis,

new

^species.

Body

elongated,narrow, gradually taperingposteriorly.

Head

with frontal margin produced into a semiconvex, subtriangulate

median

rostralprocessbetweenthe basaljoints ofthefirstantennae.

Eyes

large, reddish brown, occupyingocular processes articulatedtothe head.

The

^first pair of antennae has a peduncle of

two

articles, the basal one relativelystout

and

slightlylongerthanthedistal.

The

biramoseflagellum consists of a superiorbranch

composed

of seven slender articles,

and

an

22—

Proc. Biol.Soc.Wash.,Vol.36,1923. (147)

equalinferiorbranch

composed

ofsevenarticles; allthe^{joints of}theanten- naearesetwithlonghairs.

The

greaterantennaeareaboutaslongasthe head.

The

secondantennae extendslightly

beyond

thesecondjoint ofthe peduncle of the ^first antennae

and

consist of apeduncle of twoslender articles

and

a flagellum^offourrings.

The

peduncleofthesecondantennae

issparselysetwithlonghairsbutthereisnoscalepresent.

Thorax:

The

^firstsegmentofthe thoraxiscoalescedwiththe head,form- ing a carapace^;thesecondisalittleshorterthanthosefollowing,the third

and

fourth are subequal, each being a littlelonger than the second; the fifth,sixth

and

seventhareaboutequal,eachbeingabout one

and

one-half times aslong asthe second segment.

The

lateral margins of the third, fourth, fifth,sixth

and

seventhsegmentsare distinctlycleft

and

the post- lateral anglesof the seventh segmentare decidedly producedposteriorly.

Epimera

dorsally distinctonthelastfoursegments,extending the posterior half ofthelateralmargins.

The

gnathopods are slender, in the normal position curving over the mouthparts, notextending

beyond

the anteriormarginofthe head.

The hand

^ischubby, the

thumb

being thick

and

bluntlypointed

and

thefinger slender

and

decidedly curved, the tip being quite pointed

and

the inner margin finely serrate.

The

second, third, fourth,

and

fifth pairs of legs aresimilar in structure,beingrelatively

weak and

graduatingly decreasing in size posteriorly.

The

lastthreejoints ofeachlegareflattened, blade- shaped, withthe innermarginsdenselysetwithlongspines, the terminal jointbeing tippedwiththreedistinctspineswithlesserspinesinterspersed.

Epipodytesarepresent,theyspringfromthe basaljoint oftheleg

and

are directed obliquelyposteriorly,thedistalendsreachingalmosttothe

median

ventralline.

Each

epipodyteisshapedlikealong slenderblade,terminat- ingina subtriangulatepoint,the threeposteriorepipodytes are narrower.

Abdomen:

Allsixsegmentsare distinct, the first, second

and

third are narrow, subequal, the fourth

and

fifth are wider, subequal, having the postlateral angles posteriorly produced.

The

telson is shield-shaped, havingtheposteriormarginbluntlyrounded.

The

uropodaarisefromthe ventral surfaceofthetelson;thefirstjointisrudimentary, thesecondisa squarish,flatblade,bearing afew^finehairsalong the margin. Threepairs ofpleopodaare present

and

havethebrancheswell-developed.

The

holotype

was

collected at

Laguna

Beach,California,

by

Dr.William A. Hilton,

who

donated^ittothe collections oftheUnitedStatesNational

Museum.

Order:

ISOPODA.

Superfamily: cymoithoidea.

Family:

Anthuridab.

Genus: Edanthura, new.

First fivesegmentsof

abdomen

distinct inbothsexes. Flagellaofboth pairs ofantennae rudimentaryinbothsexes. Mouthpartswell-developed, witharticulationdistinctly differentfromthatofthe othergeneraof this family.

Type: Edanthura^linearis,

new

speciesfrom

Laguna

Beach,California.

Boone — -New Marine Tanaid and Isopod

Crustacea.

149

Edanthuralinearis,

new

^species.

Body

narrow, subcylindric, linear, surfacesmooth, color lightyellow.

Head

rectagular, longerthan wide with frontalmargin witha distinct

median

point; anterolateral angles decidedly produced terminating in a point that reaches almost to the distal endof thepeduncle of the first antennae. Eyesdistinct,elliptical,setobliquelyinthe anterolateral angles of the head.

The

^first antennae consist of a peduncle

and

rudimentary flagellum.

The

second antennae are similar with a slight difference in size. Mouthpartswell-developed, unique.

Thorax:

The

^firstsixsegments are squarish, thefirst, second

and

third beingaboutequal, thefourth,fifth

and

sixthbeingaboutequal,eachofthe latterbeingslightlylongerthan

any

ofthe former, theseventhsegmentis

about one-half as long as the first.

The

first

and

second segments are narrower posteriorly with the line of segmentation emphasized. Legs:

the^firstpairaregeniculate, relatively short, stout, subchelate,havingthe firstjointlong, produced outwardlikea shoulder, the secondresemble a stout forearm, the thirdisquiteshort,thefourth,fifth

and

sixthtaper

and

terminateina curvedpointeddactyl. Fourpairs ofmarsupialplatesare present, theyareverythin,transparent, squarishwiththefreeedgesvery slightlyroundedatthecorners.

Abdomen:

This consists of six distinctsegments

and

is slightlylonger than thelast

two

thoracic segments taken together; the firstsegment is

hiddendorsally

by

^thesevenththoracicsegmentbeing distinguishable only laterally

and

ventrally;thesecond

and

thirdsegmentsarenarrow, similar

and

subequal; the fourth segment is similar butslightly wider than the precedingsegment^; thefifthsegmentresembles thefourth,thetelsonisas longasthe outeruropoda

and

isV-shaped

and

fringedwithhairs. Uro- poda:

The

^superiorbranchoftheuropodaoverarch thetelson,but do not quite

meet

inthe dorsalcenter, theyare

somewhat

convex

and

are directed obliquelysidewise, combining withtheinferioruropoda

and

other features ofthe telsonincreatingafanlike aspect. Thereisadistinctlycleftincision ontheextremeposteriormargin,whichgivesthe superioruropoda decided- lybilobed aspect; theinferiorbranchoftheuropodisaslongasthetelson, relatively narrow basally, widening distally, the posterior margin being straight;thefirstjointterminatesabouttheposteriormarginofthe superior uropod.

The

uropoda

and

telsonareheavily fringedwithlongfinehairs.

The

pleopodaare slender

and

heavily fringedwithfine hairs.

Thisspecies

was

collectedat

Laguna

Beach, California,

by

Dr. William Hilton,

who

withcharacteristic generositydonatedit tothe collections of theUnitedStatesNational

Museum.

Superfamily:

Sphaerominae

^. Genus:

Exosphaeroma.

Exosphaeroma

aphrodita,

new

species.

Animal

exquisitelysculptured

and

ornamented, iridescent pearly, fairy- like initsetherealbeauty.

Head

strongly convex, anteriormargin rounded

and

ornamented

by

a

150 Proceedings

_oftheBiological Society of

Washington.

prominent

median

tubercle on each side of which is a lesser elongate tubercle;along theposteriormarginthereisa

row

offive,similar,subequal elongate tubercles. Eyes prominent, elliptical, composite, occupying the postlateralangleofthe head.

The

firstantennae havethe

two

peduncular jointsenlarged,stout,subequal,

and

a flagellumoffour shortjointswhich takentogether areaboutaslongasthesecond peduncularjoint.

The

^first antennae extend abouttothe anteriormarginofthefirstthoracicsegment

The

second antennaeareaslong ora^triflelongerthanthefirstantennae

The mouth

parts aretypicalExosphaeroma; the second third

and

fourth articles ofthe palpofthe maxillipeds areverydecided produced.

Thorax:

The

^firstsegmentislongerthanthehead

and

bears a transverse

row

consisting of five similar, equal, hemispherical tubercles along the anterior margin, evenly spaced,eachonein linewiththe elongate tubercles ofthe head; thereis also a transverse

row

ofsevensimilarhemispherical tubercles along the posteriormargin^{of this}segment;the second, third

and

fourthsegmentsaresimilar

and

subequal,eachbearingatransverse

row

of sevensimilarhemispherical tuberclesplacedin linewiththeposterior

row

oftubercles ofthe ^firstsegment

and

situatedalong theposteriormargins ofthe respectivesegments;thefifth

and

sixthsegmentsareslightlylonger than the precedingones, subequal, eachornamented with a

row

of seven hemispherical tubercles placedas onthepreceding segments; theseventh segmentislongerinthe

median

area

and

has the posteriormargin produced to a prominent

median

tooth giving the segment a triangulateeffect; on either side of this

median

toothseparated

by

a small recurvate spaceisa small toothwhichin turnisseparated

by

awiderrecurvate space from another tooth intermediate insize.

The

epimera are well developed, closelyap- pressed to the segments,

and

havingthe dorsal surface decidedlyconcave forminga groove, theepimeraofthefifth

and

sixthsegmentshavetheouter marginal edge decidedly curled over

and

inward; the sixth epimera are decidedly produced posteriorly.

The

^legs are ambulatory, similar

and

subequal.

Abdomen:

Thisconsists of

two

closelyfused segments; thefirstsegment resembles theseventh thoracic segment havingthe posterior marginpro- ducedtoa

median

tooth

and

with

two

lesserteethon eachside asonthe seventh segment.

The

telsonisproducedtriangulatelywiththeapex^slightly rounded. ^Itiselevatedrooflike inthe

median

dorsalline

and

has thesides sloping

and

terraced; there are four small dentitions inthe anterior region forminga V-like design;posteriortothese are eight smaller dentitionsforming a wider V; succeeding thisisa prominentlineofsutureroughlyparalleling the^lateralmargins ofthesegment; thereis asecondshorter, lessdistinct line of suture close tothe lateralmargin. These suture lines unitein a tridentate pattern near theapexofthetelson. Pleopodaone,

two and

three bearnostylet,aresimilar,subequal

and

heavily fringedwithhairs. Pleo-

poda

four

and

five havesubequal, ovate, fleshybranches with transverse ridges. Pleopodaare identical inboth ^sexes.

The

uropodaarise atthe baseof the telson

and

are closelyappressedthereto; theyarevery

much

expanded, being

more

than twice as wide ^distally as basally; the inner branchhas thedistalmarginbluntlyrounded, the outerbranch producedto

Boone — New Marine Tanaid and Isopod

Crustacea.

151

a slightlytriangulate apex

and

is slightlycleft or channeled on eachside

midway

between the apex

and

the lateral margins.

The

outer lateral margin ^of the outerbranch of the uropoda is strongly bent

upward and

curvedoverinward

upon

the dorsalsurface.

The

type

and

additional materialwerecollected at

La

Jolla, California,

and

are in the collections ofthe United States National

Museum.

This species is at once distinguished from all described Sphaerominae

by

^its

exquisite sculpturing

and

ornamentation.

Out

of

many

thousands of specimensof IsopodawhichIhave examined, thisspeciesisprobably the mostbeautiful.

Dtnamenella Hansen

1905.

Dynamenella

conica,

new

species.

Body

oval, convex, surface coarsely granular, ground coloryellowish dustedwithblack.

Head

abouttwiceaswideas long,withfrontalcontour relatively straight,heavilykeeled,belowwhichthemarginisnarrowlypro- duced withthefrontaledge

marked by

anarrow,

median

truncate point, oneither side ofwhichisaU-shapedincision, followed

by

astraightarea that extends to the anteriorpart ^of the eye.

The

firstantennae have a peduncleofthree stout,subequalarticles

and

a flagellum^of three slender articles, distallytippedwithafewhairs;itextendsalmost tothe anterior margin of the third thoracic segment.

The

second antennae have a peduncle^offive,slender,subequalarticles

and

aflagellumofninefinerings, eachbearingan almosttuft of hairs,

and

extendingtothe anteriormargin ofthe fourth thoracic segment.

The

second, third

and

fourtharticlesof the palpofthe maxillipeds areproduced inwardly into lobes.

The man-

dible has a palp^ofthreearticles.

The

firstsegmentofthethoraxisabout¹Yi times^aslongas

any

ofthe followingsegments-which are subequal.

The

^firstsegmenthas thelateral marginsheavily ridged;theepimeraoccuron the second to seventh seg- mentsinclusive

and

havetheouter anglesrounded.

The

legsarenormal;

the first three pairs are directed anteriorly, the last four are directed posteriorly.

The

^distalthreejoints ofeachlegare

somewhat

sparsely

and

irregularly setwithfineshorthairs.

The abdomen

^is

composed

of

two

segments; the penultimate segment does not

show

linesoffusion;ithas the

median

arearoundlyproduced,with a strong ridged carination along the

median

posteriormargin,oneither side ofwhichisanacuteincisionformingapoint,thence strongly arcuatewith theextremepostlateralangleproducedtoaroundedpoint, resembling the epimeraoftheseventh thoracicsegment.

The

telson isstrongly convex, triangulate, with the postlateral margins infolding, funnel-like around a narrowsub-ellipticalaperture,whichisincompleteonthe ventralside;the entire posterior margin is heavily carinated, the aperture margin being finelycrenulatealso.

The

dorsalsurfaceisornamented

by

apair ofstrong ridgesthat extend almosttothe anterior

end

ofthe funnel like aperture.

These ridges are separated

by

a deep groove-like depression

and

each is followed

by

a

row

consisting ofthreeconvextubercles,thecentraltubercle being minutelylarger

and

equidistantfromthe other two, the threeforming

152 Proceedings

oftheBiological Society of

Washington.

alineequalinlength

and

depthtotheabovecited ridges,from which they areseparated

by

adeepgroove-likedepression equal tothe

median

depres- sion. These rowsofthree tubercles are followed

by

alessdistinct

row

con- sisting of

two

smallindistincttuberclesthe anterioronebeingnear thebase oftheuropoda,theposteriorbeingonalinewiththemiddletubercleofthe adjacent row.

The

uropodaconsist ofabrief,swollenpeduncle

and two

similar subequal, subovate branches which extend slightly

beyond

the posteriormarginofthetelson.

The

pleopodaarenormal.

Both

sexes of thisspeciesare known.

They

areverysimilar, differing onlyinthat thesecondpleopodaofthemalebears astylet,

and

the brush- like tufts ofsetaeonthe flagellum^oftheantennaeofthemaleare

more

pro- nounced,while the tuberclesonthe

abdomen

^ofthefemaleareweaker

and

sometimesrelativelyinconspicuousbut always distinct.

The

present species is the fourth representative of this genus to be reportedfrom the

West

Coast of

North

America;incidentally it

may

be notedthat

Monterey

Bay, California,thetypelocality ofthe three previ- ously described species, is also the firstlocality from which the present speciesisrecorded. InJune, 1905,Dr.^J.E. Benedict,^oftheUnitedStates National

Museum

secured

two

specimensatPacificGrove,

Monterey

Bay, Cat. No.50413, U.S.N. M., but owingto theirimperfect conditionIhave selectedastypeaspecimenfromthe materialsecured

by

theUnitedStates

Bureau

ofFisheriessteamerAlbatross duringthe biologicalexplorationsof

San

Francisco Bay, 1912.

The

type comes from

Red

Rock, middle

San

Francisco Bay, Aug. 3, 1912, Cat. No. 50414, U. S. N.

M.

Additional materialsecured

by

the

same

cruiseisinthecollection oftheUnitedStates National

Museum

as follows: Cat. No. 50415,

Key Route

Pier, Aug. 3, 1912, 1 specimen;Cat.No. 50416, SausalitoFerrybuilding, onpile, 1sp.;

Cat. No. 50417, Bonita Point, betweentidemarks, Aug. 1, 1912, 1 speci- men.

Dynamenella conicais atoncedistinguishedfromthe other

members

of thegenus

by

therowsoftuberclesonthetelson.

Sphaerominae Eubranchiatae.

Clianella,

new

genus.

Firstantennae withbasal articles swollen, sculptured, dovetailingwith the sculptured, carinated frontal margin of the head. Basal joint of antennulae normal, not expanded in a free plate. Without processes onthorax.

Abdomen

withapexbisected

by

adeepchannelwhich widens at the anterior

end

intoacrescentsurrounding anoverhangingblunt tooth.

The

postlateralwallofthetelsonisproducedtoa greaterdepth belowthe uropoda than above

and

isbroadlythickened

and

rounded

and

distinctly excavated.

The

uropoda are subsimilar, extending

beyond

the telson

which

theyentirelysurroundexceptinthe

median

area,wheretheirinner marginsprolong the channel; the anterolateralmarginof the outer blade slightlysurroundingthe inner blade.

The

pleopodaone,

and

pleopodatwo, each bear

an

appendixmasculina.

The endopoda

ofpleopods threeisone

jointed.

Genotype. Clianella elegans, collectedat

La

Jolla,Calif.

Boone — New Marine Tanaid and Isopod

Crustacea.

153

Clianellaelegans,

new

species.

Body

ratherbroadlyelongate, ovate,moderatelyvaulted.

The

headisnearly twiceaswideas long,iswiderposteriorly

and

has the frontalmargin producedina rimlike carinationwhich^issculpturedfrontally todovetailwiththe antennae.

The

eyes areverylarge,round,occupying the entire anterolateral areas.

The

superior antennae arise beside the clypeus,havethefirstjointelongate, swollen,sculptured, thesecondjoint alsoswollen

and

sculpturedbutnot quitehalf aslongasthefirstjoint,the thirdjointisaboutaslongasthe second,but

much

slenderer,

and

aflagel-

lum

^ofaboutfourteensubequalrings,whichreachabout

midway

thefirst thoracic segment.

The

^inferior antennae hasthe first, second

and

third joints short,subequal, the fourthjointtwiceaslong asthethird,the fifth joint slightly longer than the fourth

and

a flagellum of sixteen subequal ringseachofwhichbears a smallbrushofsetaeonthe anterior^distalmar- gin.

The

second antennaereachesnot quitetothe posteriormarginofthe third thoracic segment.

The

second, third

and

fourth^{articles of}thepalp ofthe maxillipeds are producedinto lobes.

The

firstthoracicsegmentisaboutaslonginthe

median

areaasthehead

and

has the anterolateral areas decidedly convex

and

the anterolateral angles producedclosely aroundthe ocular lobes.

The

secondtoseventh segmentsinclusiveare subequal.

The

epimeraarecompletely fusedwith the respective segments.

The

seventh thoracic segment bearsa

median

transverse

row

ofcloselyspacedgranulations.

The

firstabdominal segmentisapproximately one

and

one-halftimesas wideinthe

median

areaasthesevenththoracicsegment. Ithas thelateral area produced a ^trifle

beyond

the thoracic marginal line

and

curiously thickenedventrally.

A

vague minutelineinthe anterior areajust inside thelateralangulation ^ofthesevenththoracic segmentindicates coalesced segments, this line vanishes in the

median

lateral region but reappears indistinctly inthe central region.

A

^second, pronounced lineindicating coalescence occurs on the posterior lateralregion

and

follows the curved posterior margin of the first abdominal segment

and

vanishes rather abruptly.

Two

rows ofalternately spaced,

somewhat

largergranulations transversethissegment.

The

terminalsegmentissubtriangulatewiththe anterior two-thirdsmoderately convex

and

dividedintolobes

by

amoderate

median

longitudinal depression.

The

apexis bisected

by

adeep channel which widensatthe anteriorendintoa crescentwhich surrounds anover- hanging blunt, round, toothlike projection.

The

incision is quite deep, being nearly one-thirdaslongasthetelson.

The

marginsofthe channel arefinely crenulate.

The

postlateralthirdofthetelsonisa slopingborder definitely, closely appressed to the uropoda

and

slightly ridged at this point, viewed^{ventrallythis}postlateralwallofthetelsonisproducedtoa greater depthbelow theuropoda than above; this producedparthas the outer wall convex,widening

and

thickeningtowardthebaseoftheuropod, ridged along the extreme ventral margin

and

thence the internal wall is slightly rounded

and

excavated to\form the pleopod cavity.

The

^first

and

second pairs of pleopoda each bear an appendix masculina.

The

thirdpleopoda have the exopod one-jointed, the fourth pleopoda have aleaf-likeexopod

and

an

endopod marked by heavy

transversefolds,the fifthpleopodahavealeaf-likeexopod

and

the

endopod more

heavily

marked by

transversefoldsthanthatofthe fourthendopod.

The

uropodaaresub- similar, ariseatthebaseofthe teson

and

arecloselyappressedthereto,they are larger, very

much

expanded, being one

and

one-half times as wide distallyas basally, broadlyroundeddistallywiththemarginfinely crenu- late.

They

extend

beyond

the telson a distance approximatelyequal to two-fifthsthelengthof thesinus, buttheirrespectiveinnermargins con- tinue themarginalwallofthesinus, thus accentuating the channel.

The

outer branch viewed ventrally is decidedly convex, its anterior lateral marginslightlyover-arching the innerblade.

Six specimenswere collectedfrom the debris from bunches of mussels along the outer ledge of rocksnorth of Scripps Institution for Biological Research,

La

Jolla, California,Oct. 23, 1915.

The

type, Cat.No. 50421, U.S. N. M.,

and two

paratypesare inthecollections oftheU.S.National

Museum;

three additionalparatypes arein the collections of the Scripps Institution for Biological Research. Anotherrepresentativeof the

same

species

was

collectedat PointWhite,

San

Pedro,California,

May

18,1919,

by Mr.

E.P.

Chace and

donatedtotheU.S. National

Museum,

Cat.

No.

50422.

Superfamily: Idotheoidea.

Erichsonella pseudoculata,

new

species.

Body

rectilinear, about three

and

ahalf times aslongaswide.

Head

wider thanlong,withfrontalmargin producedtoa depressed blunt triangu- lar

median

rostrum betweenthe antennalforamina

and

withthe anter- lateral angles produced hornlike,

somewhat

flaring; the

median

lateral margin ^is roundly excavate

and

the postlateral angleis occupied

by

the small sphericaleyes;the

median

dorsalsurfaceof theheadis convex

and

produced^{anteriorlyinto}

two

conical,forward-projecting,hornlike tubercles which extend

beyond

the

median

frontalmarginof the head.

The

first

antennaeare short reaching onlytothe^distalendofthesecondjoint ofthe second antennae

and

havethe basal joint entirely

and

the secondjoint almost entirely hidden, the third jointis veryswollen

and

has its distal margin producedresembling therostral joint;the fourth

and

fifthjointsare slenderer,subequal,widerdistally

and

the flagellumisclavatebutbearing 7 or 8indistinct minute markings^ofcoalescence,

and

afringe ofhairson the distal margin.

The

second antennae are very conspicuous, being nearlyhalfaslongasthe

body and

decidedlygeniculate,thefirstarticleis quite inconspicuous, thesecondarticleis quite broad,wideninganteriorly

and

havingthedistalmarginrecurvatelikeflowerpetals,the third^article isaboutaslongasthe second,butisflattened,thefourthistwiceaslong asthethird,thefifthisaboutaslongasthe^third,allhavethedistalmargin recurvate

and

producedinto points;the flagellum^isclavate, aboutas long asthe fourthjointofthepeduncle

and

hasafringe of finehairsonthedistal end.

Thorax:

The

first thoracicsegment^is

somewhat

shorterinthe

median

Boone — _New Marine Tanaid and Isopod

Crustacea.

155

areathan

any

^ofthe following

and

has the

median

anteriormarginslightly bilobate

and

the anterolateral angles decidedly acutelyproduced

and

pro- jectingwiththeapex notched

and

theentireprocess shining black, giving the appearanceof hugetriangulate eyes.

The median

dorsallineis pro- duced into

two

ridgelike tubercles placed one behind the other.

The

second, third, fourth,fifth

and

sixththoracicsegmentsareaboutequal,the seventh segment is slightly shorter than those preceding; each has the

median

dorsalline ridged

and

a single tubercle on the

median

posterior margin.

The

epimeral plates are very small, bilobate, scarcely visible dorsallyonthefirstsegment,butaredistinctonthesecondtoseventhseg- ments^inclusive. Thoseofthe second, third

and

fourthsegmentsaresmall, triangulate,

and

placedunder

and

occupypartofthe anterior half ofthe marginofthesegment, thefifthepimeronisslightlywider

and

situateda

little

more

posteriorly, the sixth

and

seventh epimera are quite large, occupyingthe entireposteriorhalf of themargin of theirrespective seg- ments

and

being longer

and

directedbackward, whereasthe otherepimera are quite short

and

aredirectedstraightoutwards.

The

legsareall

ambu-

latory, similar

and

subequal

and

havethe dactyli biunguiculate.

The abdomen

isvaulted, shield-shaped,

and

is

composed

ofasingleseg-

ment

butbears a decided lateral incision

and

single distinct, incomplete suturelineindicating thefusedfirstsegment;thispartis quitenarrowin the lateral regionbuthas the centralportion strongly ridged

and

gently produced, being nearlyfivetimesaslonginthe

median

dorsallineas inthe lateralline;threeslightbutdistincttuberclesalong the

median

ridgeindi- catethe areasofthe completely fused second,third, fourth

and

fifthseg- ments; the telsonistypicallyshield-shapedwiththe centralareavaulted

and

the suggestion of a

median

^line extending clear to the apex of the posteriorend; the posteriormarginisproducedintoa

median

pointwhich

isstrong

and

acute; extending decidedly

beyond

thelateral angles which are almost absolute right angles.

The

uropoda have the apical joints triangulate,aboutone-fifth aslongasthepeduncularjoint,

and

eachuro-

pod

bears

two

distinctnodules along theline ofunionofthe

two

joints;the peduncularjointhasthefree lateralmarginheavily grooved.

The

species

may

beatonce distinguishedfrom ^all the

American

Erichsonellas

by

its

huge

and

curiousfalseeyes; also

by

the presenceofalateralincisionon the

abdomen.

The

type, aunique specimen, Cat.No. 50420 U. S. N. M., comes from

San

Pedro,California,

and was

collected

by Mr.

E.P.Chace. Itisinterest-

ingtonote thatthisisthefirstErichsonellareportedfromthe

West

Coast of

North

America, the three otherAmerican

members

of thisgenusbeing fromtheEastCoast.