CRUSTACEA CASPIA. 429 



The posterior paiys of coxal plates are much less deep than the anterior, 

 and successively diminish in size. The antepenultimate pair have the ante- 

 rior lobe somewhat deeper than the posterior, and evenly rounded at 

 the tip. 



The epimeral plates of the metasome are well-developed, the 1st pair 

 being, as usual, rounded, the 2 posterior pairs nearly rectangular. The uro- 

 some is rather short and stout, and highly remarkable by the great eleva- 

 tion ot the posterior edge of the 1st segment above the level of the 2nd. 

 On the most prominent place 2 small juxtaposed denticles occur, and beside 

 these, there is, on the same segment, a small lateral spine. In P. affinis, 

 this segment, like the others, is quite smooth, and in P. fcmorafa it gives 

 rise to the peculiar forked dorsal process, characteristic of that species. 



The eyes are (see fig. 3) very small, and of a somewhat irregular oval 

 form, with the pigment rather light. 



The antennae resemble in structure those in the 2 other species, being 

 rather strongly built, and subequal in length, with a number of finely cili- 

 ated setae issuing from the hind edge of the outer peduncular joints. The 

 superior ones about equal in length the cephalon and the 3 first segments 

 of the mesosome combined, and have the 1st joint of the peduncle very 

 large, exceeding in length the other 2 combined. The flagellum (see fig. 2) 

 about equals in length the peduncle, and is composed of 9 articulations, the 

 1st of which is much tiie largest. The accessory appendage somewhat ex- 

 ceeds in length the last peduncular joint, and is composed of 3 well-defined 

 articulations. 



The inferior antennse are somewhat more strongly built than the superior, 

 almost pediform, and have the 3 outer joints of the peduncle rather thick, 

 with densely crowded bristles both anteriorly and posteriorly. The flagellum 

 is about the same leugtii as that of the superior antennae, and is composed 

 of a similar number of articulations. 



The anterior gnathopoda (fig. 5) have the carpus rather broad and ex- 

 panded, though not nearly so much as in P. femorata. The propodos is con- 

 siderably narrower than the carpus, and oblong oval in form, with the palm 

 quite short, aud imperfectly defined below. In the other 2 species the palm 

 is much more elongated, occupying the greater part of the inferior edge. 

 The dactylus is comparatively very small. 



The posterior gnathopoda (fig. 6) are more slender and elongated than 

 the anterior, with the propodos oblong linear in form, and having the palm 

 transverse, the lower corner being rectangular, not, as in the other 2 spe- 

 cies, produced to a thumb-like prominence. 



The 2 anterior pairs of pereiopoda are of quite normal structure. 



^H3,-UiiT. oTp. 259. 9 



