AMPHIPODA. 95 



and pinnated(l); cylindrical, articulated appendages to the posterior 

 extremity of the body. 



Apseudes, Leach. — Eupheus, Risso. 



The thorax also divided into several segments, but the two ante- 

 rior feet terminated by a didactyle forceps; the two following ones 

 claviform, ending in a point and dentated on the edges; the next 

 six slender and unguiculaled at the extremity; the last four natatory. 

 The antennae are simple. The body is narrow, elongated, and has 

 two long setaceous appendages at its posterior extremity(2). 



The third and last section — Decempedes, Lat. — is composed of 

 Amphipoda, which present but six distinct feet. 



Typhis, Risso. 



But two very small antennae, the head large and eyes not promi- 

 nent; each pair of feet annexed to its peculiar segment, and the four 

 anterior terminated by a didactyle forceps. On each side of the 

 thorax are two movable plates, forming a sort of lids or valves, 

 which when joined, the animal folding up its feet and tail beneath, 

 enclose the body inferiorly and give it a spheroidal appearance. 

 The posterior extremity of the tail has no appendage(3). 



Anceus, Risso. — Gnathia, Leach. 



The thorax divided into as many segments as there are pairs of 

 feet, but all the latter simple and monodactyle; four setaceous an- 

 tennae; a stout square head with two large projections in the form of 

 mandibles; extremity of the tail furnished with foliaceous fin-like 

 appendages(4). 



(1) According- to the figure of Slabber — Oniscus arenarius, Encyclop. Method., 

 Atl. d'Hist. Nat, CCCXXX, 3, 4, — the number of feet is but eight; reasoning from 

 analogy, I presume it to be fourteen; besides, if the figure be exact, this genus 

 would belong to the next section. 



(2) Eupheus ligioides, Risso, Crust., Ill, 37; Desmar., Consid., 285; — Apseudes 

 talpa. Leach; — Cancer gammarus talpa, Montag., Trans. Lin. See, IX, iv, 6; Des- 

 mar., Consid.: XLVI, 9. See the Gammarus heteroclitus, Viviani, Phosphor. 

 Maris, II, ii, 12. 



N.B. The genus Rhcea, M. Edwards, Ann. des Sc. Nat. XIII, xiii. A, 292, dif- 

 fers from the preceding in the superior antennae, which are stouter, longer, and 

 bifid. 



(3) Typhis ovoides, Risso, Crust., If, 9; Desmar., Consid., p. 281, XLVI, 5. 



(4) Anceus forficularis, Risso, Crust., IT, 10; Desmar., Consid., XLVI, 6; — An- 

 ceus maxillaris; Cancer maxillaris, Montag., Trans. Lin. See, VII, vi, 2; Desmar. 

 lb., XLVI, 7. 



