270 CRUSTACEA. 



united inferiorly, and folded laterally over the post- abdomen, enve- 

 loping it like a case ; those of the first and tliird pairs are \ingiii- 

 culated ; the second feet are terminated byl two short and obtuse 

 toes *. 



There, the body is oval, without salient caudiform appendages, 

 composed of threads or fin-like productions at its posterior extre- 

 mity. A portion of the superior teguments forms a shield, which 

 does not cover its anterior half, is rounded and emarginated before, 

 widened and as if bilobate behind ; then follow three pieces or scales, 

 posteriorly rounded and emarginated, the second of which, and the 

 smallest of the three, is almost in the form of a reversed heart ; the 

 last, and the largest, is arched. The four posterior feet are in the 

 form of lamincie, and are united by pairs ; those of the first and the 

 third are unguiculated ; the extremity of the second is bifid. The 

 siphon is apparent. The ova are covered by two large, oval, conti- 

 guous, coriaceous pieces, placed under the abdomen, and surpassing 

 it in length. Such are the characters of the genus 



Cecrops, Leach, 



Of which a single species only is known. 



Cecrops Latreillii, Leach, Encyc. Brit., Supp. I, xx ; 1,3, the 

 male ; 2, 4, the female ; 5, the antennae magnified; Desmar., Con- 

 sid. L, 2 Found on the branchiae of the Tunny and Turbot. 



The second tribe, that of the Lerneiformes, Lat., consists of Ento- 

 'mostraca, which approximate to the Lerncae, in their external confi- 

 guration, still more than the preceding subgenera. There are but 

 ten feet visible f, mostly very short, and but slightlyor nowise adapted 

 to natation. Sometimes the body is nearly vermiform and cylindrical, 

 the anterior segment being merely somewhat widened and furnished 

 with two projecting didactyle claws ; sometimes, on account of two 

 lateral expansions resembling lobes or wings behind the thorax, and 

 of two posterior ovaries, it forms a small quadrilateral mass. This 

 tribe is composed of two genera. In the first or the 



DiCHELESTiuM, Hevm., Juv. 



We observe a narrow elongated body, slightly dilated before, and 

 composed of seven segments, the anterior of which — the thorax of 

 Herm. — is wider than the others, rhomboidal, and formed of the 

 head and a portion of the thorax united. It bears : l,four short 

 antennae, of which the lateral are filiform and consist of several joints, 

 and the intermediate project like little arms and are quadri-articu- 

 lated, the last joint terminating in a didactyle claw ; 2, an inferior, 

 membranous, and tubular siphon ; 3, three kinds of defonned palpi — 



* Anthosoma Smithii, Leach; Desmar., Consid., L, 3 ; CalUjus imhricaius, Risso. 

 t There are probably two more, as in the preceding subgenera, but they are either 

 indistinct or have such a peculiar form that they have not been recognised. 



