T. XHiJ CRUSTACEA CASPIA. 491 



The general form of the body (see figs. 1 and 2) is rather slender and 

 elongated, with the anterior division well marked off from the posterior, the 

 length of which it does not nearly attain. As seen from above (fig. 1), this 

 part of the body exhibits an oblong oval form, with the greatest breadth about 

 in the middle, and but very slightly tapering to each extremity. In a lateral 

 view (fig. 2) it somewhat approaches to a clavate form, tapering more dis- 

 tinctly posteriorly than in front. The dorsal face is but very little arched, 

 exhibiting, however, a somewhat irregularly indented aspect, on account of 

 the projecting branchial regions, and the sharp demarcation of the free seg- 

 ments of the mesosome. 



The carapace is not very large, scarcely exceeding in length the exposed 

 part of the trunk. It exhibits in a lateral aspect (fig. 2) an oval quadrangu- 

 lar form, with the upper contour nearly horizontal and somewhat irregular, 

 on account of the sharp demarcation of the branchial regions. The latter 

 have, along their most prominent part, a distinct and slightly serrated crest, 

 which anteriorly, at the limit of the gastric area, is suddenly bent down, 

 thus causing at this place a notch, as it were, in the upper contour. The 

 gastric region has 2 parallel keels along the middle, likewise slightly ser- 

 rated, and terminating each in front with a small dentiform projection (see 

 fig. 3). The ocular lobe is very broad and transversely truncated in front. 

 The pseudo-rostral projection exhibits a very remarkable and unusual shape, 

 being divided into 2 vertical, juxtaposed, thin lamellae (see fig. 2), which are 

 somewhat upturned and evenly rounded at the tip. When the animal is viewed 

 from above (figs. 1 and 3), these lamellse are found to be separated by a rather 

 wide and deep sinus, and only quite posteriorly a small transverse apophysis 

 is seen issuing from the inside of each lamella, both meeting just in front 

 of the ocular lobe (see fig. 3). The antero-lateral corners are rather broad, 

 nearly rectangular, and have their anterior edge minutely serrate. The 

 inferior edges of the carapace exhibit a rather strong curve in front of the 

 middle. 



The exposed part of the trunk does not exhibit any keel or dorsal pro- 

 jections, though its upper face appears somewhat jagged, on account of the 

 sharp demarcation of the segments (see fig. 2). The 2nd and 3rd segments 

 have their dorsal part rather short, but both expand considerably on the 

 sides, forming broad laminar epimera. The last 2 segments are comparatively 

 large and massive, and resemble those in P. tenuicauda. 



The metasome is much more fully developed than in that species, and, 

 as above stated, considerably longer than the anterior part of the body. 



The integuments are slightly incrusted, and exhibit everywhere a con- 

 spicuous squamous structure. 



Bulletin N. S. IV (XXXVI) p. 327. 



