400 GAMMA RIM. 



AMPHIPODA . OAMMARIDES. 



NATATOEIA. 



Genus MEGAMCERA. 



Megamcera. SPENCE BATE, Cat. Ampli. Brit. Mus. p. 224. 



Oammarus (Division A. a a.). MILNE EDWARDS, Hist, des Crust, iii. p. 48. 

 Gammarus (Division -j- 2). LILJEBORG, Ofvers. af Kongl. Vet. 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 Mcera 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. 



