CRUSTACEA CASPIA. ■ 455 



Tlie pereiopoda are ratlier slender, aud have their outer part edged 

 with scattered fascicles of spines (see fig. 5). The basal joint of the ante- 

 penultimate pair (fig>6) does not differ much in shape from that of the 

 penultimate pair (fig. 7), though being somewhat shorter. The basal joint 

 of the last pair (fig. 8) is mucli larger, forming posteriorly a lamellar ex- 

 pansion, which is produced below to an obtusely-pointed lappet. The hind 

 edge of the joint is but very slightly curved, and is distinctly S(!rrated. 



The 2 anterior pairs of uropoda (fig. 10) exhibit the usual structure, the 

 rami being nearly equal-sized, aud tipped by numerous short spines. 



The last pair of uropoda (fig. 9) are rather elongated, though not quite 

 attaining the length of the urosome. The outer ramus is very narrow, sub- 

 linear, and is densely fringed all round with slender setae, besides having 

 on each side 3 fascicles of short spines. Its terminal joint is so very minute 

 as easily to escape attention. The inner ramus exhibits the usual rudimentary 

 condition. 



The telson (fig. 11) is comparatively small, and has the lateral lobes 

 narrowly truncated at the tip, each carrying 3 apical spines accompanied 

 by a few small hairs. 



Occurrence. — Some few specimens of this form were collected by 

 Dr. Grimm in the middle part of the Caspian Sea, from a depth of 35 

 fathoms. 



15. Gammarus tenellus, G. 0. Sars, n. sp. 



(PI. 7,'figs. 12-22). 



Specific Characters. — Body extremely slender and compressed, with 

 the raesosome and metasome quite smooth. Cephalon with the lateral lobes 

 very obliquely truncated, so as to form in front an acute cornei'. Coxal 

 plates not very large. Last pair of epimeral plates of metasome acutely 

 produced at the lateral corners. Urosome distinctly spinulose above, the 

 spinules being upturned, and arranged in dorsal and lateral fascicles. Eyes 

 well-developed, oblong oval. Antennae rather slender, both pairs being 

 densely fringed with delicate setse, the superior ones much the longer, with 

 the flagellum twice as long as the peduncle, and the accessory appendage 

 4-articulate. Gnathopoda in both sexes subequal in size, being in female 

 rather feeble, in male somewhat stronger. Pereiopoda moderately slender, 

 and edged with dense fascicles of bristles, basal joint of last pair scarcely 

 differing either in size or shape from that of the penultimate pair. Last 

 pair of uropoda very much elongated, considerably exceeding in length the 

 urosome, outer ramus sub-linear and edged with dense fascicles of spines, 

 inner ramus very small. Telson small, and abruptly narrowed in its outer 



$H3.-MaT. CTp. as5. 35 31* 



