(XXXVI)] CKUSTACEA CASPIA. 63 



5. Mesomysis intermedia, Czern. 



(PL VI). 



Mesomysis intermedia. Czerniavsky, I. c. fasc. 2, p. 52, PI. XXII, figs. 14 — 20, PI. XXIII, 

 figs. 1—15. 



Specific Characters. — Form of body (see PI. VI, fig. 1) nearly as in 

 M. Czerniavskyi. Carapace having the cephalic part about as broad as the 

 1st segment of metasome, anterior edge evenly arched in the middle, frontal 

 spine uncovered (see fig. 2). Eyes (ibid.) of the usual pyrifonn shape and 

 projecting laterally somewhat beyond the sides of the carapace, corneal part, 

 as seen from above, reniform in shape. Antennal scales (see fig. 3) exceed- 

 ing the peduncles of the superior antennae by considerably more than Vg 

 of their length, and oblong rhomboidal in form, the ape.x being rather obli- 

 quely truncated, witli the terminal part in front of the outer corner (see fig. 

 4) occupying more than '/j of the length of the scale, apical segment well 

 defined. Pereiopoda (fig. 6) rather slender, with the ischial and meral joints 

 comparatively less dilated than in the other species, tarsal part scarcely 

 longer than the meral joint, dactylar joint (fig. 7) of the usual structure. 

 Pleopoda (fig. 12, 13) scarcely diifering from those in the other species, 

 except that the outer ramus of the 3rd pair in male (fig. 1 2) appears somewhat 

 smaller, scarcely exceeding half the length of the inner. Telson (fig. 8) about 

 the length of the last segment of metasome, and ratlier attenuated distaliy, 

 lateral edges nearly straight, and armed each with from 1 6 to 19 spinules, 

 the outmost of which is not far remote from the tip, apical sinus (see fig. 9) 

 quite obsolete, the terminal edge being transversely truncated and bordered 

 with a regular series of 14 acute dentiform projections, spines of the outer 

 corners not very strong. Inner lamella of the uropoda (fig. 10) considerably 

 tumefied at the base, with the otolith very large, inner edge armed, below 

 the marginal sette, with 4 spines only, the outmost of which is rather remote 

 from the apex. Body without any distinct dendritic ramifications, tliough 

 having the usual dorsal pigmentary centres. Lengtli of adult female scarcely 

 exceeding 12 mm. 



Ttemarlcs. — The present species has been rather imperfectly described 

 and figured by Mr. Czerniavsky, and as I moreover have not had an op- 

 portunity of examining his type specimens, I should have been in considerable 

 doubt about the identity of the species here described, if there were not a 

 single very prominent feature, in whicli both forms would seem perfectly to 

 agree, viz., the peculiar want of any true apical sinus on the telson, its apex 

 being transversely truncated, though exhibiting the usual comblike arma- 

 ture of the edge. Besides this characteristic, the present species is easily 

 distinguishable from the 3 preceding ones by the much more obliquely trun- 



Melanges biologiqiies. T. XIII, p. 411. 



