4 Amphipoda 



P. A. Latreille (1802, Hist. Crust. Ins., v. 3 p. 38) was the first who united all 

 species knowu to him of Amphipoda (as at present understood) in one group, the family 

 of Gammariuae, to the exclusion of all other species; later (1816, in: Nouv. Dict., ed. 2 

 V. 1 p. 467) he devised for the group the uame Amphipoda, separating, however, the 

 genera Cyamus and Caprella as Laemodipoda. The limits of our order, generally 

 accepted to-day, were settled by Krayer (1843, in: Naturh. Tidsskr., ü. 4 p. 490) and 

 J. D. Dana (1852, in: Amer. J. Sei., ser. 2 v.l4 p. 297); from the latter author is 

 derived also the division of the Amphipoda into the 3 tribes of Gammaridea, Hyperiidea 

 and Caprellidea. Only Gerstaecker (1883 & 86, in: Bronn's Kl. Ordn., f.5ii p. 283, 481) 

 regards the Tanaidea as a tribe of Amphipoda. 



Synoptical diagnosis of the three legions: 



Head not fused with Ist segment of peraeon. Palp 

 o f m a X i 1 1 i p e d 2- to 4-j o i n t e d. Peraeon with 7 pairs of legs^ 

 5 or 6 Segments of peraeon with branchial vesicles; 4 segments 

 in ? with marsupial plates; Ist joiut of gaathopods 1. 2 

 and of peraeopods 1-5 forming or united to well developed 

 side-plates. Pleon consisting usually of 7 free seg- 

 ments, carrying 3 pairs of pleopods and usually 

 3 pairs, at least 1 pair, of uropods; uropod 1 always 

 with2rami. Eyes varying in size and form, — 4 in number. 

 Hepato-pancreatic tubes 4, rarely 2; rectal glands 2 or 1, 

 sometimes rudimentary. Heart with 3 pairs, rarely 1 pair, of 



Ostia. Nerve-chain with 4 ganglia in pleon-segments 1—4 I. Leg. Qammaridea 

 Head not fused with Ist segment of peraeon. Maxilli- 

 ped without palp. Peraeon with 7 pairs of leg^3 — 5 (6?) 



Segments of peraeon with branchial vesicles; 4 segments in$ 



with marsupial plates; Ist Joint of gnathopods 1, 2 and of 



peraeopods 1 — 5 small or wanting. Pleon consisting 



usually of 7 free segments, with 3 pairs ofpleopodsv/ 



and 3 pairs of uropods -^rami of uropods often evanescent. 



Eyes usually of large size. Hepato-pancreatic tubes 2 or 



none; rectal glands none. Heart with 2, rarely 3, pairs of 



Ostia. Nerve-chain with 3 or 4 ganglia in the anterior 



segments of pleon II. Leg. Hyperiidea 



Head fused with Ist segment of peraeon. Palp of 



maxilliped I- to 4-jointed. Peraeon often with fewer 



than 7 pairs of legs; 2, rarely 3, segments of peraeon with 



branchial vesicles; 2 segments in $ with marsupial plates; 



Ist Joint of gnathopods and peraeopods wanting. Pleon 



and its legs rudimentary. Eyes small, 1 pair. Hepato- 

 pancreatic tubes 2 ; rectal glands none. Heart with 3 pairs 



of Ostia. Posterior ganglia of nerve-chain very small, none 



situatedin pleon III. Leg. Caprellidea 



