210 G. 0. SAKS, 



last 3 (St. 54, 55, 56) at some distance north and west of the last-named 

 island. 



In the collection of Dr. Grimm this species is only represented by a 

 few specimens collected in the Bai of Baku, from a depth of 2—3 fathoms. 



The species is, as yet known, restricted in its occurrence to the 

 Caspian Sea. 



Gen. 4. Gammarus, Fabr. 



Remarks. — Of all the Amphipodous genera represented in tlie Caspian 

 Sea, this comprises the greatest number of species. In the collection of 

 Mr. Warpachowsky I have distinguished no less than 11 different species, 

 and in the collection of Dr. Grimm several additional species are repre- 

 sented. Whereas the hitherto known species of Gammarus., in the restriction 

 of the genus now generally adopted, exhibit a very uniform appearance, the 

 Caspian species partly diverge rather markedly in their character from the 

 type, both as regards the outward appearance and tlie structure of the 

 several appendages. Thus the Gammarus caspius Pallas, to be described 

 below, is highly distinguished by the segments of metasome being produced 

 dorsally to similar acuminate projections to those occurring in the genus 

 Amathillina, and whereas in the earlier known species of Gammarus, the 

 superior antennae are invariably very slender and considerably longer than 

 the inferior, in several of the Caspian species they are rather much reduced 

 in length, so as not at all exceeding the inferior ones in size. Moreover the 

 last pair of uropoda sometimes are unusually short, and in all the Caspian 

 species as yet examined their inner ramus is very small and scale-like. The 

 most normally looking species is that described below as Gammarus haemo- 

 bapJies Eichwald. 



6. Gammarus caspius, Pallas. 



(PI. VII). 



Gammarus casjnus Pall., Eichwald: «Fauna caspio-caucasia nonnullis 

 observationibus novis illustr.)). Nouv. Mem. de la Soc. Imp. des Naturalistes 

 de Moscou, T. VII, 1842, p. 230. 



Syn.: Gammarus semicarinatus, Sp. Bate. 

 » Gammarus Byhowskyi., Grimm MS. 



Specific Characteristic. — Body moderately slender, Avitli the segments 

 of mesosome generally smooth, though in some specimens the last one is 

 slightly keeled above and produced at the posterior edge to a small denti- 

 form projection, those of metasome provided with well-marked posteriorly 



*U3.-MaT. CTp. 210. 32 



