84 CRUSTACEA. 



angular dilatation, and their posterior extremity exhibits two 

 teeth(l). In 



Alima, Leach, 



The first joint of the ocular pedicles is slender, cylindrical, and 

 much longer than the following one: the body is narrower and more 

 elongated than that of an Erichthus; the lateral borders of the shield 

 are nearly straight or are but slightly dilated; there is a slight 

 longitudinal carina on its middle, and each of its angles forms a 

 spine, the two posterior of which are the largest(2). 



FAMILY II. 



BIPELTATA. 



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

 the anterior 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 fili- 

 form, 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 antennae exhibits no scale ; 

 the intermediaries are terminated by two threads. The ocu- 

 lar pedicles are long. The body is much flattened, mem- 

 branous, and diaphanous ; the abdomen small and its posterior 

 fin without spines. It comprises but a single genus, the 



9 



Phyllosoma, Leach, 



Of which all the species inhabit the Atlantic Ocean and Oriental 



seas(3). 



(1) Erichthus vitreus, Lat. See art. Squille, Atl. d'Hist. Nat. of the Encyclop. 

 Method., pi. cccliv; and Desmar. Consid., XLIV, 2, 3. 



(2) Alima hyalina, Lat., Encyclop. Method., art. Squille, and Ibid. Atl. d'Hist. 

 Nat., CCCLIV, 8; Desmar., Consid., XLIV, 1. 



(3) See Encyclop. Method., and Nouv. Diet. d'Hist. Nat., Ed. II, article Phyl- 

 losome,- also the work of Desmarest on the Crustacea and the Zoology of the Voy. 

 de Freycinet. As respects their nervous system, the Phyllosoma: seem to be in- 

 termediate between the preceding and subsequent Crustacea. See Audouin and 

 Edwards, op. cit. 



