4 AMPUIPODA NORMALIA. 



Group NORMALIA. 



The coxje of the peroiopoda are squamiformlj developed, generally 

 large enough to protect the branchial sacs. The pleon is normally de- 

 veloped. Tlie three anterior pairs of pleopoda consist of ciUated, 

 double-branched, multiarticulate, flexible appendages, which are used 

 in swimming, and originate on the ventral surface. The three pos- 

 terior pairs of pleopoda consist of stiff", generally double-branched 

 stylets, of which the last pair vary more than the others, and some- 

 times have the spines developed into hooks. The telson is formed 

 of a single or double, unimportant, minute plate, sometimes furnished 

 with hook-like spines. This group comprises the Order Amphipoda, 

 as described by M. IVIilne-Edwards, It is divided into Gammarina 

 and Hyperina. 



Division GAMMARINA. 



The upper antennae consist of a peduncle of three joints and a 

 multiarticulate flagellum, with sometimes a secondary appendage 

 originating at its base. The lower antenna) consist of a peduncle 

 of five joints (of which the first two are more or less fused together 

 and bear the olfactory denticle) and a flagellum. The maxillipeds 

 cover the preceding appendages of the mouth. One or both of the 

 gnathopoda are subchelate. This division is sjmonymous with M. 

 Edwards's family of Crevettines, and that of Gammaridea of Dana. 

 It is subdivided into Vagantia and Domicola. 



Subdivision VAGANTIA. 



The lower antenna terminate like the superior ; the spines upon 

 the posterior pleopoda are never developed into hooks, but generally 

 into fine hau's, except in the Saltatoria. They eonstmct no home 

 to rest in, but move from place to place, some swimming or crawling 

 in the sea, others hopping along the shore. This subdivision repre- 

 sents M. Edwards's tribe of Satjteurs, It consists of the two tribes, 

 Saltatoria and Natatoria. 



Tribe Saltatoria. 



The posterior pair of pleopoda never exceed the preceding in 

 length. The hairs on the entire animal are short and stifi". The 

 mode of progression when out of the Avater is by leaps. The habits 

 of the animals are terrestrial or subaquatic. This tribe contaius but 

 a single family. 



Fam. 1. ORCHESTIDJE. 



The upper antennae are shorter than the lower, and not furnished 

 with a secondary appendage. The mandibles are without an ap- 



