400 
GAMMARIDiE. 
AMP HIP OD A. 
NATATORIA. 
GAMMARIDES. 
Genus — MEGAMCERA. 
Megamcera. Spence Bate, Cat. Amph. Brit. Mus. p. 224. 
Gainmarus (Division A. a a.). Milne Edwards, Hist, des Crust, iii. p. 48. 
Gammarus (Division + 2). Liljeborg, Ofvers. af Kongl. Yet. Akad. 
Forhandl. 1853, p. 452. 
Generic character. Dorsal surface of the pleon without 
fasciculi of spines. Eyes round. Superior antennae longer 
than the inferior. Gnathopoda subchelate, the second pair 
being the larger. Posterior pair of pleopoda biramous, the 
branches generally equal-sized. Telson double. 
This genus bears a near resemblance to that of Gam- 
marus . It has, however, been considered sufficiently dis- 
tinct to be arranged, both by Edwards and Liljeborg, in a 
separate division. It does not possess the fasciculi of spines 
planted upon the dorsal surface of the last three caudal 
segments, which we consider to be characteristic of the 
genus Gammarus. The eyes in this genus are generally 
round ; and the second pair of legs are constantly larger 
than the first pair, and frequently different in form. 
It can be distinguished from the genus Moera by the 
greater depth of the coxae, by the relative proportions 
of the hand of the second pair of legs, and generally by 
the greater length of the posterior pair of caudal 
appendages. 
