ISOPODS OF NOETH AMERICA. 11 



Color brown, marked in some specimens with a darlvor ])rown, and 

 having- oval patches of the darker color on the head. 



Kyska Harbor, Alaska; Dr. W. H. Dall, collector; depth, 6 to 12 

 fathoms. 



Type.—C^t. No. 22563, U.8.N.M. 



TANAIS ROBUSTUS Moore. 



Tanais robustus Moore, Proc. Acad. Nat. Sci. Phila., 1894, pp. 90-94, pi. v. — 

 Richardson, American Naturalist, 1900, XXXIV, p. 211; Proc. U. S. Nat. 

 Mus., 1901, p. 501. 



Locality. — New Jerse3^ 



Found "inhabiting- minute tubes in the crevices between the scales 

 of the turtle's (Thalassochelys caretta) carapace. When unmolested 

 these little crustaceans could be seen crawling- carefully about among- 

 their fellow voyagers or lying- at the mouths of their domiciles with 

 only the head and chehe projecting; when disturbed they promptly 

 retreated out of sight." — Moore. 



"It is quite r()l)ust for the family, being- less than 3i times as long 

 as broad. The carapace, which is the broadest portion of the body, 

 is terminated anteriorly b}' a minute rostrum, whilst its posterior border 

 is somewhat concave in the middle line. In front of the origin of the 

 great gnathopods the lateral outline is strongly concave, but opposite 

 the bases of these lim])s it becomes swollen. When viewed dorsally, 

 the carapace appears in general figure top-shaped. Two grooves, one 

 on each side, indicate upon the dorsal surface the inner boundary of 

 the branchial chamber. Behind the carapace the breadth of the body 

 becomes gradualh' less with each successive segment. The fourth free 

 segment of the person is the longest, slightly exceeding the third, 

 which is in turn longer than the fifth. 



"The y)leon is composed of six distinct segments, of which the 

 fourth and fifth are nnich shorter than the others and the sixth is 

 terminated posteriorly b}^ a blunt median projection. The body is 

 constricted at the joints and the segmentation is distinctly marked. 

 The dorsal surface is furnished laterally with a few seti^, which on 

 the first and second segments of the pleon form a short row on each 

 side, but never form a transverse band crossing- the segment. 



"The e3'es and e} e-lobes are large, the latter being let into deep 

 recesses in the anterior lateral portion of the carapace. 



"The antennuhe consist of three joints, of which the bas;d one is 

 somewhat longer than the other two combined. A small knob (rudi- 

 mentary fiagellum) terminates each. In the male the antennula usually 

 a])Out equal in length the carapace with the fii'st free segment, but are 

 sometimes consideral)ly longer. In the female the}^ are about equal 

 to the carapace alone. 



