GAMMARUS MARINUS. 
371 
Gammarus gracilis. Rathkb, Fauna der Krym. t. v. fig. 7-10, 1837. 
Spence Bate, Rep. Brit. Assoc. 1855. Ann. 
Nat. Hist. 11 ser. xix. p. 144. 1857. White, 
Pop. Hist. Brit. Crust, p. 184. 
Gammarus pcecilurus. Rathke, Nov. Act. Acad. Leop. xx. p. 68, t. 4, 
fig. 2. Liljeborg, Kongl. Yet. Akad. Forhandl. 
1853, p. 450. Ofvers. af Kongl. Yet. Akad. 
Forhandl. 1855, March, No. 16. Bruzelius, 
Skand. Amph. Gramm, p. 54. 
Gammarus Kroyeri. Rathke, Nov. Act. Acad. Leop. xx. p. 68, t. 4, 
fig. 2. Liljeborg, Ofvers. af Kongl. Yet. Akad. 
1851, p. 22. 
This species was first described by Dr. Leach in 
vol. xi. of the Linnaean 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 antennae 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 antennae 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 antennae 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 
