CRUSTACEA. 215 



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 apjn-iula^i 1 . Tlir other four foot-jaws are very small and 

 conical. Tim base of the lateral antennae exhibits no scale; the 

 intermediaries are terminated by two threads. The ocular pedicles 

 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 



PHYLLGSOMA, Leach, 

 Of which all the species inhabit the Atlantic Ocean and Oriental 



snas * 



MALACOSTRACA. 



b. Eyes sessile and immoveable. 



The Branchiopoda are the only Crustacea of which we shall hence- 

 forward have occasion to speak, that exhibit eyes placed on pedicles. 

 But independently of the fact that these pedicles are neither articu- 

 lated nor lodged in special cavities, the Branchiopoda have no shell, 

 and are otherwise removed from the preceding Crustacea 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 

 of articulations of which each of the first seven is furnished 

 with a pair of feet, the following and last ones, seven at most, form- 

 ing a sort of tail terminated by fins or styliform appendages. The 

 -rnts four antennae, the two intermediate superior, two eyes, 

 and a mouth composed of two mandibles, a tongue, two pairs of jaws, 

 and a sort of lip formed by two foot-jaws that correspond to the two 

 i ior ones of the Decapoda ; here, as in the Stomapoda, the 

 flagrum no longer exists. The four last foot-jaws are transformed 



* See Encyclop. Method., and Nouv. Diet. Hist. Nat., Ed. II, article Phyl- 

 tosome ; also the work of Desmnrest on the Crustacea and the Zoology of the 

 de Frcycinet. As respects their nervous system, the Phyllosomo: seem to be in- 

 termediate between the preceding and subsequent Crustacea. See Audouin and 

 Edwards, op. cit. 



