ox CRUSTACEA. 233 



solid, lateral pieces, compressed, and trenchant internally, 

 carrying on their back, and near their point of articulation, an 

 appendage or palpus formed of three articulations ; these man- 

 dibles being placed anteriorly, and underneath all the other 

 even pieces : 3rd. with a thin, lamellate, and bifid tongue, 

 placed against the posterior basis of the mandibles : 4th. with 

 a first pair ofjaws, membranaceous, deeply lobate, and ciliated 

 on their edges, without palpi, and applied on the lower face of 

 the mandibles : 5th. with a second pair ofjaws, without palpi, 

 applied on the first, equally membranaceous, lobate, and cili- 

 ated : 6th, with a third pair of membranaceous jaws, provided 

 externally with a palpus, formed of a long peduncle, which 

 carries at its extremity a small arched stalk, setaceous and 

 multi-articulate : 7th, with a fourth pair ofjaws, formed by a 

 stem rather narrow, compressed, not membranaceous, divided, 

 like the feet, into six articulations, and by an external flagelli- 

 form palpus, analogous to that of the preceding jaws, but more 

 distinct : 8th. with a last pair of pieces, composed like the 

 preceding, of two parts or stems ; the interior, crustaceous and 

 compressed, is divided into six articulations, of which the second 

 and third are much larger than the others, and the last small ; 

 the exterior is in the form of a palpus similar to those of the 

 two pair ofjaws which are situated before these last. 



M. Savigny considers these three pair of external jaws as 

 nothing but feet, so modified as to serve for manducation, and 

 his opinion is founded upon this, that the palpus with which 

 they are provided is analogous to the threads remarked in the 

 anterior feet of many entomostraca, that the two external ones 

 are articulated like feet, properly so called, and generally com- 

 posed of the same number of pieces, and that at the base they 

 serve as a point of attachment for the gills like ordinary feet. 

 According to this naturalist, all the true Crustacea should have 

 sixteen feet, and not differ among themselves, but in the 

 number of those feet which are thus converted into auxiliary 



