312 CRUSTACEA. 



FAMILY II. 



BIPELTATA. 



In this family we find the shell divided into two shields, the ante- 

 rior of which, very large and more or less oval, forms the head, and 

 the posterior, corresponding to the thorax, transverse and angular 

 in its circumference, supports the foot-jaws and feet. These latter, 

 with the exception at most of the two posterior and two last foot-jaws, 

 are slender and filiform, usually very long and accompanied by a 

 lateral ciliated appendage. The other four foot-jaws are very small 

 and conical. The base of the lateral antennsE! exhibits no scale; 

 the intermediaries are terminated by two threads. The ocular pe- 

 dicles are long. The body is much flattened, membranous, and 

 diaphanous; the abdomen small and its posterior fin without spines. 

 It comprises but a single genus, the 



PiiYLLosoMA, Leach, 

 Of which all the species inhabit the Atlantic Ocean and Oriental seas. 



MALACOSTRACA. 



h. Eyes sessile and immovable. 



The Branchiopoda are the only Crustacea of which we shall 

 henceforward have occasion to speak, that exhibit eyes placed on 

 pedicles. But independently of the fact that these pedicles are 

 neither articulated nor lodged in special cavities, the Branchiopoda 

 have no shell and are otherwise removed from the preceding Crus- 

 tacea by various characters. All the Malacostraca of this division 

 are also deprived of a shell; their body, from the head downwards, 

 is composed of a suite of articulations of which each of the first 

 seven is furnished with a pair of feet, the following and last ones, 

 seven at most, forming a sort of tail terminated by fins or styliform 

 appendages. The head presents four antennae, the two intermediate 

 superior, two eyes, and a mouth composed of two mandibles, a 

 tongue, two paii's of jaws, and a sort of lip formed by two foot-jaws 

 that correspond to the two superior ones of the Decapoda; here, as 

 in the Stomapoda, the flagrum no longer exists. The four last 



