42 NEW-YORK FAUNA — CRUSTACEA. 
ORDER V. ISOPODA. 
Body more or less depressed, divided into segments varying in number from three to seven. 
Head distinct from the first segment of the body. Mandibles without palpt. Mouth 
with three pair of jaws. Feet ten to fourteen. Tail of one or more segments, supporting 
the branchia. Eyes sessile. 
GENUS IDOTEA. Fabricius. 
Body oblong-ovate. External antenne moderately long, setaceous ; the peduncle with four 
joints, and the extremity many-jointed: internal antenne placed slightly above the outer, 
small, filiform. Head subquadrate. Two sessile eyes. ‘Tail large, of three segments, the 
last without any terminal appendices, and covering the branchie and the two lamine which 
protect them. Feet subequal. 
IpDOTEA CAGCA. 
Idotea ceca. Savy, Journ. Acad. Nat. Sciences, Vol. 1, p. 424. 
ig id. Gouxp, Invertebrata of Mass. p. 337. 
Description. Body oblong-oval, broadest at the third or fourth segment, attenuated behind. 
Head quadrate, depressed, with a deep fissure on the sides. Antenne approximated at the 
base. First segment of the tail short; second somewhat trilobate ; last segment nearly or 
quite half the length of the body, attenuated to an acute conic point, subcarinate above. 
Three anterior pairs of feet robust, monodactyle; the remainder simple, unarmed, and with 
rigid hairs. Nails of the hind pairs rectilinear. Eyes inconspicuous. 
Color, whitish varied with brown dots, occasionally confluent into bands; eyes milk white ; 
head with a transverse black band. 
Length, 0°3-0°5. 
This little species occurs on all sandy shores from Massachusetts to Florida, where it forms 
the little serpentine tracks noticed in the sand. The figure of the J. tricuspis of Europe 
(Pl. 9, fig. 35), is introduced to illustrate the genus, as no opportunity has presented itself of 
figuring the American species. 
