REPOET ON THE SCHIZOPODA. 209 



The specimen examined by V. Thompson, and also those described by Milne- 

 Edwards and Kroyer, were from the Atlantic. Dana collected the species {^Siriella 

 vitrea and Siriella hrevipes) in the Pacific. The specimens examined by Professor Clans 

 were derived from the Museum in Hamburcr : locality not recorded. 



Distribution. — According to the localities stated above, the present species would 

 seem to have a very extensive geographical distribution, ranging, as it does, throughout 

 the North and South Atlantic, the Australian Seas, and the Pacific Ocean. 



54. Siriella gracilis, Dana (PI. XXXVI. figs. 25-28). 



Siriella gracilis, Dana, United States Exploring Expedition, Crustacea, i. p. 6-58, pi. xliv. 



figs. 1, a-!j. 

 Siriella gracilis, G. 0. Sars, Preliminary Notices on the Challenger Schizopoda, No. 51. 



Specific CJiaracters. — Form of body somewhat more slender than in Siriella, 

 thompsoni. Frontal plate triangular, less acute. Last caudal segment as long as the two 

 preceding taken together. Eyes much smaller than in preceding species, cornea scarcely 

 expanded at all, and occupying but a small part of the eye. Antennal scale rhomboidal, 

 apex very obliquely truncate, inner corner projecting. Propodal joint of legs distinctly 

 subdivided into two articulations, terminal claw very elongate. Telson linguiform, aj)ex 

 evenly rounded, with a small tridentate plate issuing between the last pair of elongate 

 spines. Uropoda with outer plate but slightly shorter than inner, and having a smaller 

 number of spines at the exterior edge. Length about 6 mm. 



Remarks. — The present species may be easily distinguished from the preceding by a 

 somewhat more slender form of body, the less developed eyes, and the deviating form of 

 the antennal scale and of the telson. 



Description. — The length of the largest specimen in the collection does not exceed 

 6 mm., and this species is hence of rather smaller size than the preceding. 



The form of the body (see PL XXXVL fig. 25) appears somewhat more slender than 

 in Siriella thompsoni, though not nearly to such a degree as in certain other species of 

 the genus. 



The carapace exhibits a form very similar to that in Siriella thompsoni, but has the 

 frontal projection somewhat less pointed and triangular in form. 



Of the caudal segments, the last is rather elongate, about as long as the tv\-o preceding 

 segments taken together. 



The eyes are far from so fully developed as in Siriella thompsoni, being but very 

 slightly expanded at the end, with the cornea occupying a comparatively small part of 

 the eye. 



The antennular peduncle would seem to have the last joint relatively shorter than in 

 the preceding species, but for the rest it exhibits a very similar structure. 



The antennal scale (fig. 26), on the other hand, is very difterent, being comparatively 



(ZOOL. CHALL. ESP. — PAET XXXVII. — 1885.) Oo 27 



