CRUSTACEA CASPIA. 211 



pointiug dorsal projections. The 2 anterior segments of urosome having each 

 a much elevated tubercle, transversely truncated at the tip and armed with 

 4 strong apical spines arranged in pairs; last segment with a single small 

 spinule on each side of the dorsal face. Cephalon with the rostral projection 

 extremely small, nearly obsolete, lateral lobes rather broad and obtusely trun- 

 cated at the tip. Anterior pairs of coxal plates but little deeper than the corre- 

 sponding segments and rapidly increasing in size to the 4th, which are much 

 expanded in their outer part, with a very distinct emargiuation posteriorly. 

 The last 2 pairs of epimeral plates of metasome rather large and acutely 

 produced at the lateral corners. Eyes well developed and of an oblong form, 

 slightly instricted in the middle. Superior antennae very slender and much 

 longer than the inferior, joints of the peduncle rapidly diminishing in size, 

 flagellum nearly twice as long as the peduncle, accessory appendage well 

 developed and 5 -articulate. Guathopoda in both sexes rather unequal in 

 size, the posterior ones being much the larger; those in male being, as usual, 

 more powerful than in female, with the propodos rather large, especially in 

 the posterior ones, palm in both pairs somewhat oblique and nearly straight. 

 Pereiopoda moderately slender and edged in their outer part with spines 

 and delicate bristles, antepenultimate pair much shorter than the last 2 

 pairs, which are nearly equal in length, basal joint of last pair not much 

 expanded and oblong quadrangular in form, with the posterior edge dis- 

 tinctly serrate. Last paii- of uropoda reaching considerably beyond the 

 other, inner ramus small, squamiform, outer ramus rather elongated and 

 edged with long ciliated setse and a few fascicles of spines. Telson of mode- 

 rate size and cleft to the base, each half armed at the tip with 2 small 

 spines and a few delicate bristles. Length of adult female 13 mm., of male 

 16 mm. 



Remarks. — The diagnosis given by Eichwald in the above-cited 

 work does not leave any doubt, that the above-characterised form is tliat 

 originally recorded by Pallas as Gammarus caspius. Under the latter name 

 Sp. Bate, in his Catalogue of Amphipoda in the British Museum, describes 

 a very different form, whereas I am much inclined to believe that the form 

 recorded by him in the same work (without any locality) as G. semicarinatus 

 is that here treated of. In Dr. Grimm's collection this species is labelled 

 G. Byhoivskyi n. sp. From all other known species this is at once recognized 

 by the strong dorsal projections of the metasome. In spite of this anomalous 

 feature, it is a true Gammarus, as shown by the structure both of the oral 

 parts and the other appendages. 



*u3.-JIaT. CTp. 211. S3 '■^ 



