T. Xlll] - CRUSTACEA CASPIA. 407 



antennal scales, the uniform structure of the pereiopoda, and by the very 

 shallow apical sinus of the telson, and its peculiar comb-like armature. Mr. 

 Czerniavsky refers to this genus 5 species, one of which, M. Kröyeri, 

 should, however, perhaps more properly be placed within the genus Austro- 

 mysis, whereas another form described by that author as a Paramysis, must 

 find its place in the present genus. As far as yet known, the genus is not 

 represented beyond the Caspian and Black Seas, one of the species, M. la- 

 custris, having, however, been found in a lake among the mountains of 

 Caucasus. In the Caspian Sea the genus is represented by 5 species, one of 

 which is now for the first time established. 



2. Mesomysis Ullskyi (Czerniavsky). 

 (Pi. III). 



Paramysis Ullskyi 1 ) Czerniavsky, 1. c, fasc. 2. p. 65, PI. XXVI, figs 13 — 23. 



Specific Characters. — Body (see PI. Ill, fig. 1) very slender and elon- 

 gated, with the anterior division rather attenuated in front, and scarcely longer 

 than the 4 anterior segments of metasome combined. Carapace deeply emargi- 

 nated posteriorly, leaving the dorsal part of the last 2 segments of mesosome 

 uncovered, cephalic part scarcely as broad as the 1st segment of metasome, and 

 having the anterior edge nearly straight; frontal spine large, uncovered. Me- 

 tasome very elongated, and gradually tapering posteriorly. Eyes of moderate 

 size, projecting somewhat beyond the sides of the carapace, corneal part rather 

 expanded and distinctly emarginated on the dorsal face. Peduncles of the 

 superior antennae (fig. 2) conspicuously club-shaped, the last joint being con- 

 siderably dilated and having at the inner corner about 10 strong plumose 

 setse. Antennal scales (see fig. 3) of middle size, exceeding the peduncles of 

 the superior antennse by about 1 / i of their length, form oblong linear, the 

 breadth equalling l / z of the length, terminal part projecting beyond the 

 outer corner occupying about 1 J 1 of the length of the scale, apical segment 

 well defined, bearing 5 of the marginal setse (see fig. 4). Pereiopoda (fig. 11) 

 moderately slender, with the meral joint a little shorter than the ischial 

 one, tarsal part somewhat longer than the former, with the 1st joint much 

 shorter than the other 3, which are nearly equal-sized, dactylar joint (see 

 fig. 12) very small, with the terminal claw nearly setiform. Telson (fig. 14) 

 comparatively large, exceeding somewhat in length the last segment of me- 

 tasome, and gradually tapering distally, lateral edges nearly straight, and 

 armed each with from 18 to 22 spinules, the outermost of which is some- 



1) It may be noted, that this species in other parts of the work has been termed Para- 

 mysis Strauchi, and that the type specimens are labelled in accordance therewith. 



Bulletin N. S. IV (XXXYI) p. 59. 



