CRUSTACEA CASPIA. 353 



11. Gammarus compressus, G. 0. Sais, u. sj). 



/ (PI. XI, figs. 1 — 10). 



Specific Characters. — Body moderately slender and very much com- 

 pressed, Avith the hack smooth throughout. Lateral lobes of cephalou but 

 slightly projecting, and narrowly rounded at the tip. Anterior pairs of coxal 

 plates rather large and densely fringed with bristles distally; 1st pair very 

 much expanded in their outer part; 4tli pair large, about as broad as they 

 are deep. The last 2 pairs of epimeral plates of metasome but very slightly 

 produced at the lateral corners. Urosome comparatively short and quite 

 smooth above. Eyes not very large, narrow oblong in form. Antennae com- 

 paratively short and nearly equal-sized, the superior ones having the 1st 

 jdint of the peduncle very large and massive, flagellum but little longer 

 than the peduncle, accessory appendage 3-articulate. Gnathopoda in female 

 small and feeble, and nearly equal-sized. Anterior pairs of pereiopoda com- 

 paratively strongly built, and densely setous, with the meral joint not a 

 little expanded, especially in the 2nd pair; the 3 posterior pairs rather 

 slender and nearly equal in length; basal joint of last pair moderately ex- 

 panded and regularly oval in form. Last pair of uropoda with the inner 

 ramus less rudimentary than in tlie preceding species, being nearly half as 

 long as the outer, the latter liaving the terminal joint well developed. 

 Telson fully as long as it is broad at the base, each half with 2 apical 

 spines. Length of adult female 7 min. 



Bemarhs. — This new species is chiefly characterised by its extremely 

 compressed body, the short, equal-sized antennae, the form of the 1st and 

 4th pair of coxal plates, and the structure of the last pair of uropoda. As 

 of the preceding species, only female specimens have hitherto come under 

 my inspection. 



Description of (he female. 



The lengtli of fully adult, ovigerous specimens measures about 7 mm., 

 and accordingly this form must also be reckoned among the smaller species 

 of the genus. 



The form of the body (see fig. 1) is rather slender and very much com- 

 pressed, with the back narrowly rounded and smooth throughout. 



The cephalon about equals in length the first 2 segments of the meso- 

 soine combined, and appears neai'ly transversely truncated in front, the 

 lateral lobes projecting but slightly, and being narrowly rounded at the tip. 



The anterior pairs of coxal plates are rather large and fringed on their 

 distal edge with numerous delicate bristles. Tlie 1st pair (see fig. 3) are of 



*a3.-MaT. cip. 333. 11 23 



