CRUSTACEA CASPIA. 443 



always differs conspicuously from the others by its rounded, gibbous 

 shape, is iu the present species of the very same appearance as those pre- 

 ceding it. 



The cephalon about equals in length the first 2 segments of the meso- 

 some combined, and exhibits a form similar to that in the type species, the 

 lateral lobes being somewhat prominent and transversely truncated at the tip. 



The coxal and ei)imeral plates are likewise of much the same appearance 

 as in that species. 



The urosome, however, as above stated, differs in the fact of its 1 st 

 segment having a well defined, though rather small dorsal expansion, of 

 which no trace is found in A. cristata. The last 2 segments have dorsally a 

 few small hairs, but are destitute of any true spinules. 



The eyes are pronouncedly reniform in shape, and somewhat obliquely 

 disposed, with dark pigment. 



The superior antennae exhibit the slender form characteristic of the 

 genus, and are perhaps a little more elongated than iu A. cristata. The 2nd 

 joint of the peduncle is nearly as long as the 1st, though considerably 

 narrower, and the 3rd joint is about half its length. The flagellum is almost 

 twice as long as the peduncle, and divided into numerous short articulations. 

 Tlie accessoi-y appendage (see fig. 8) is fully as long as the last peduncular 

 joint, and in the male is composed of 6 articulations. 



The inferior antennae are considerably shorter than the superior, and 

 have the last 2 joints of the peduncle nearly of e(iual length. The flagellum 

 about equals iu length those joints combined. 



The gnathopoda, as in the other species, are very different in the 2 

 sexes, being in the female (figs. 11, 12) rather small and feeble, whereas 

 in the male (figs. 9, 10) they are very powerfully developed, with the pro- 

 podos of considerable size. In structure, these limbs nearly agree with those 

 in A. cristata. 



This is also the case with the pereiopoda, though, on a closer compari- 

 son, the 3 posterior pairs are found to differ in the fact of the basal joint 

 being comparatively narrower and of nearly similar shape in the 2 sexes 

 (see figs. 7, 13, 14). 



The last pair of uropoda (fig. 15) are very short and thick, scarcely at 

 all extending beyond the others, aud having the outer ramus but little longer 

 than the basal part, and only armed with 3 short spines and a few delicate 

 hairs; its terminal joint is well defined and spiniform. The inner ramus, as 

 in the other species, is extremely small and scale-like. 



The telson (fig. 16) is short and broad, and, as usual, cleft to the base, 

 the cleft somewhat widening behind. Each of the lateral halves is only pro- 



*a3.-lIaT. OTp. 273. 23 



