CKUSTACEA CASl'IA. 293 



comparatively slender, with the meral joint not much expanded, and in male 

 densely clothed ^ith slender bristles anteriorly. Last pair of pereiopoda very 

 much elongated, exceeding half the length of the body, basal joint rather 

 expanded and, as usual, jjrovided on both edges with a double row of partly 

 ciliated seta', outer joints very slender and narrow. The 2 anterior pairs of 

 uropoda strongly built and densely spinous; last ])nir small, with the terminal 

 joint oyal lamellifoi'm and densely setiferous. Telson about twice as broad as 

 it is long, and provided at the end above with 2 lamelliform crests, each di- 

 vided into 4 recurved teeth, tip transversely truncate. Length of adult female 

 10 mm., of male 11 mm. 



licmarks. — This is the largest and finest of the Caspian species, and is 

 easily recognizable by the slender and elongated superior antennte, and by 

 the structure of tiie inferior ones. Moreover the comparatively slender form 

 of the anterior pairs of pereiopoda may serve to easily distinguish this 

 species from the other Caspian forms. 



Description. — The length of adult, ovigerous females is about 10 mm., 

 that of males 11 mm., and this form accordingly grows to a considerably 

 larger size than any of the other known species. 



The form of the body (see PL XX, tigs. 1 and 2, PL XXI, fig. 1) is that 

 characteristic of the genus, being subdepressed, with the back broadly vaulted, 

 and the lateral parts of the segments extended horizontally. As seen from 

 above (PL XXI, fig. 1), the body appears nearly of equal breadth through- 

 out, exhibiting a somewhat linear form. 



The cephalon is broad, subdepressed, and exceeds somewhat in length 

 the first two segments of the mesosome combined. The frontal edge is (see 

 PL XXI, fig. 1) angularly produced in the middle, and the lateral corners 

 project as narrowly rounded lobes between the bases of the 2 pairs of 

 antenna. Behind these lobes the lateral edges of the cephalon form (see 

 PL XX, figs. 1 and 2) a broad emargination encircling the base of the in- 

 ferior antenna;. 



The coxal plates are, as in the other species of the genus, very small 

 and scale-like. The 1st pair (see PL XX, fig. 12) are, however, somewhat 

 more fully developed, being produced anteriorly to a narrowly rounded lobe 

 clothed with numerous slender, anteriorly curving setie, some of which are 

 finely ciliated. The 3 posterior pairs are slightly bilobed, with the anterior 

 lobe the larger. 



The epimeral plates of the metas(tme are rather shallow, and all of them 

 obtusely rounded at the lateral corners, their edges being densely fringed 

 with ciliated bristles. Those of the last pair are much larger than the others 

 in accordance with the greater development of the corresponding segment. 



'ti-s.-Mai. CTp. 201. 19 



