GAMMARUS MARINTJS. 371 



Gammarus gracilis. Rathke, Fauna der Krym. t. v. fig. 7-10, 1837. 



Spence Date, Hep. Brit. Assoc. 1855. Ann. 



Nat. Hist. 11 ser. xix. p. 114. 1857. White, 



Pop. Hist. Brit. Crust, p. 184. 

 Gammarus pcecilurus. Rathke, Nov. Act. Acad. Leop. xx. p. 08, t. 4, 



fig. 2. Liljeborc, Kongl. Vet. Akad. Forhandl. 



1853, p. 450. Of vers, af Kongl. Vet. Akad. 



Forhandl. 1855, March, No. 16. Bruzelius, 



Skand. Amph. Gamm. p. 54. 

 Gammarus Krijyeri. Rathke, Nov. Act. Acad. Leop. xx. p. 68, t. 4, 



fig. 2. Liljeborg, Ofvers. af Kongl. Vet. Akad. 



1851, p. 22. 



This species was first described by Dr. Leach in 

 vol. xi. of the Linnsean Transactions. His specific 

 name has, however, been subsequently misapplied by 

 Milne Edwards to a species which does not exhibit 

 the characters of the terminal appendages as described 

 by Leach, who distinguished this from the common 

 English fresh-water species by having the head between 

 the antennas subacuminated as well as by the character 

 of the tail appendages above-mentioned. 



The first three segments of the tail have the infero- 

 posterior angle not developed to a point ; the third, 

 which is generally the most produced, is rounded in this 

 species, a form which is constantly seen to be the case 

 in imperfectly-developed individuals. The fasciculi 

 upon the three posterior segments consist of blunt 

 spines, subapically tipped with a minute cilium, arranged 

 in small bundles of two or three spines each. The 

 eyes are reniform, white, with black spots. The su- 

 perior antennas are about half the length of the animal ; 

 the flagellum is about twice the length of the peduncle ; 

 the secondary appendage consists of but three articuli. 

 The inferior antennas are about half the length of the 

 superior, and the flagellum is as long as the peduncle. 

 The first pair of legs have the hand but slightly dilated, 



b b 2 



