CRUSTACEA. 
270 
united inferiorly, and folded laterally over the post- abdomen, enve- 
loping it like a case ; those of the first and third pairs are ungui- 
culated ; the second feet are terminated byj two short and obtuse 
toes *. 
There, the body is oval, without salient caudiforra 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 laminae, 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 surjjassing 
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 antenna?, magnified ; Desmar., Con- 
sid. L, 2. Found on the branchioe of the Tunny and Turbot. 
The second tribe, that of the Lerneipormes, Lat., consists of Ento- 
mostraca, which approximate to the Lernese, 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, Herm., Jun. 
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 : 1, 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- 
latcd, the last joint terminating in a didactyle claw; 2, an inferior, 
membranous, and tubular siphon ; 3, three kinds of deformed palpi — 
* Anthosoma Smithii, Leach; Desmar., Consid., L, 3 ; Caligus imbricains, 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. 
