

HYPERIDEA. 979 



the contrary, the Gammaridea, in analogy with the Cancroids, have a 

 staid, uniform habit and structure. And we observe also, that the 

 species are more numerous among the Gammaridea and Cancroids, 

 than among the Hyperidea and Maioids or Leucosoids. 



Many of the diversities mentioned are of subordinate importance in 

 classification, as they do not affect the general grade or habits of the 

 species. The distinction between the species which have the second 

 pair of antennae extended, and those with these organs folded up and 

 concealed either side of the head or thorax — a characteristic nowhere 

 else observed among Amphipods — is of high importance. The enlarge- 

 ment, also, of the first or second of the three posterior pairs of legs, 

 and its modification so as to give one or both of them the power of 

 grasping, bestow upon such species a character and habit quite 

 diverse from those in which these legs are slender, vergiform, and un- 

 guiculate in the usual way. These legs appear to be used for grasp- 

 ing in coition. In consideration of these differences, we distribute 

 the Hyperidea into three families. 



Fam. I. Hyperid^e.- — Antennae 2dae exsertae. Abdomen in ventrem 

 se non flectens. Pedes 5ti 6ti 7mique forma longitudineque medio- 

 cres, 5tis 6tisve non percrassis nee prehensilibus. 



Fam. II. Phronimid^e. — Antennae 2dae exsertae. Abdomen in ventrem 

 se non flectens. Pedes 5ti 6tive sive crassi sive elongati, saepius 

 prehensiles, quoque otii 4tique saepe prehensiles, 



Fam. III. Typhidje. — Antennae 2dae sub capite thoraceve celatae et 

 saepius replicatae. Abdomen in ventrem saepe se flectens. Pedes 6 

 postici interdum abbreviati, articulo lmo operculiformi, interdum 

 longitudine mediocres. 



The two families, Hyperidae and Phronimidae, correspond to the 

 Hyperines Ordinaires, of Edwards (Crust., iii. 74), and the Phroni- 

 madae, of Gray (Cat. Brit. Crust. Brit. Mus., p. 56) ; the Typhidae to 

 the Hyperines Anormales of Edwards (Crust, iii. 94), or Typhidae, of 

 Gray (Cat. Brit., etc.), and the Yibilinae, to the Hyperines Gamma- 

 roides, of Edwards (Crust., iii. 72) . 



