Two new Isopods of the genus <I>Idotea</I>, from the coast of California

Vol. XII. pp. 53-55

March

24, 1898

PROCEEDINGS

BIOLOGICAL SOCIETY OF WASHINGTON

^/Cr>

^~

TWO NEW ISOPODS OF THE GENUS IDOTEA FROM THE COAST OF CALIFORNIA*

BY JAMES

E.

BENEDICT,

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

The two

species described ^{in this}

paper come within

the limits of Idotea as recognized

by

^{E. J.}

^Miers

^{in his}

monograph

^{of the}

Idoteidavj" ^Ifseveral

more

species are

found with the epimeral

characters of Idotea carinata

Lucas and

/.rodrata

here

_described, the

former

_species

may ^become

^the

type

^{of a distinct}

genus.

At

present the division

would,

ⁱⁿ

my

opinion,

be unwarranted.

Idotea rostrata _sp.

now

This_species is probably

more

_nearly related to Idotea carinata Lucas_J thanto

any

other described Idotea.

The

headisexcavatedin front; theanterodateral angles arerounded

and

_upturned.

The

_{eyes are} lateral,large

and

_veryslightly projecting.

Above

the eyes the headiselevated.

The

head _projectsforward onthe

median

line forming ^a tubercular rostrum. Inthe_largerspecimen the occipitalsutureisan _irregular impressed ^{line; theentiresurfaceof the} bead isminutelyrugose.

The

articlesof thepeduncle^{of the}antennaare short

and

stout;the length of

any

^articlenotbeing

more

than twoortwo andone-halftimes itsgreatestwidth.

The

_tiagellumon onesideiscom- posed ^ofseven stout and distinct segments, on the other side ofsix.

*Published

by

permission^ofthe Secretary of theSmithsonianInstitu- tion.

fJourn. Linn.Soc. Lond.,

XVI,

pp. 1-88, 1883.

%Lucas, ^Hist. Nat. des

Anim.

in Expl. ^Sci. Algerie, Crust., p. 60, pi.

vi, fig. 1, 1849. Miers, Journ. Linn. Soc. Lond.,

XVI,

p. 58, 1883.

12—Biol.Sue. Wash., ^Vol. XII,1898 (53)

54 Benedict — _{Two New}

Isopods from

Coast of California.

The

antennulse reach the distal margin of the thirdsegment^{of the an-} tennae; theirbasal_jointsarebroad.

The

thorax is convex

and

_nearly

smooth

; the

first,sixth,

and

seventh segments ^are about_equal inlength^; thethird, fourth,

and

fifthare broadest;

thesecondisintermediate; thefirstsegment,^{as in} carinata,^isdeeply excavated, theantero-lateral lobes reaching ^to the eyes; both lateral angles of the other segments ^are about _equally rounded.

The

epimera

show

_onlyonthe three posteriorsegments^;

on

thefifthitshows _slightly onthe middleof the margin; onthe sixthitoccupies the posterior two- thirds

ami

is quite broad posteriorly^; onthesev- enth its occupies one-half the margin

and

is tri-

angularⁱⁿform.

The

legs are moderately^slender.

With

the ex- ception of the^first pair,the basalarticlesofall havea small tubercular protuberance.

The abdomen

_taperswith the

body and

^isevenly rounded behind; it consistsofa _single segment with^{a suture} nearthe baseas in St/nidotea.

The

_operculum^isnotcrossed

by

^anoblique^line. Thereisabroadshad- ing ofpurplealong the dorsum.

The

_marginsof thearticlesof the an- tennaeand the dactyls arerosy.

Thisdescription ^is

made

from twofemales fromSan _Pedro, California, presented

by

^{Mr. S.J. Holmes.}

The

_{largerspecimen}is12

mm.

inlength.

The

sidesofbothare arcuateasisusualin thefemales ofIdotea.

Ki 12.

—

Idotea rostrata.

(X3.)

Idotea

stenops

sjx nov.

A

single large female Idotea is in thecollectionfrom Monterey, ^Cali fornia,

where

^it

was

taken

by

^Mr.

Henry

Hemphill.

In_generalappearance thespecies closelyresem- bles/.ochotensis,but

more

carefulexamination shows

it to be specifically distinct.

The

outline of the

body

^{issimilar to}that of thefemaleofochotensis.

The

headis

more

deeply excavated onthe anterior margin than ^inthatspecies.

The

_{posteriormargin}

isconcave.

The

eyes are situated a^little behindthe middle of the exposed ^lateral margin

and

are five times longerthanbroad, placed transverselyjustanterior tothe_eye, the surfaceand margin^excavated.

The antenme

are similar to those ofochotensis,

butthe flagellum has ^15articles.

The

thorax iswidestatthe third

and

fourth_seg- ments.

The

_epimeraof thesecond segment^reaches the postlateral angle

and

is

much

wider in the

Fiii. 13.

—

Idotea_stenops.

(Naturalsize.)

anterior _portion.

The

_epimera of the third

and

fourth segments are

Two New _{Isopods from}

Coast of California.

55

widestin the middle

and

cover the endsof the segments with^{the ex-} ception of the apex^{of the} posterior angles.

The

_epimeraof the fifth, sixth,

and

seventh segments^{cover the}endsofthesegments andare very wide on theirposterior margins.

The

_epimera ofochotensis are strikingly different. In the second seg-

ment

_{they occupy} the anterior half of the margin, ⁱⁿ the third about three-fifths, anil inthe fourth the anterior three-quarters.

The

_epimera of thefifth segment^coversall buttheapexof the posterior angle.

The

margins^of the sixth

and

seventh segments ^are covered

by

the epimera.

In the last three segments ^the anterior part of the epimera^is

narrow

wherein stamps^itiswide.

The abdomen

of_stenopsis

composed

of three segments. Anotherseg-

ment

isindicated

by

^asuture.

The

basal halfof the

abdomen

istaper- ing^; the_posteriorhalf hasparallel sides; the posterior angles arerounded

and

_{veryslightlyproduced}behind.

The apex

^{is acute.}

The

surfaceof the

body

^{below the}

median

line is flattened, forming an obtuse ridge fromthe base of theheadtothe

apex

^{of the}

abdomen.