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 unguiculated 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- 

 tenna; 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 1 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. Soc, 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., II, 10; Desmar., Consid., XLVI, 6; An- 

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

 lb., XLVI, 7. 



