170 CLASS CRUSTACEA. 



body is convex, and the feet are very long. But a single spe- 

 cies is known. Maia longipes, Coll. du Mus. 



If we except some species of hymenosoma, in which the tail 

 presents distinctly but four or five articulations, in all the fol- 

 lowing subgenera this part of the body has six, either in both 

 sexes or in the males. The third articulation of the external 

 jaw-feet is sometimes in the form of a reversed triangle, or of 

 an oval, narrowed inferiorly, sometimes in the form of a heart. 

 The following articulation is inserted at the middle of its 

 superior edge, or more externally than internally. 



Some, such as the three following subgenera, approach to 

 those which we have just described, in the isometrical, or at 

 least transverse form of the epistoma. The basis of the inter- 

 mediate antennae is but little remote from the upper edge of the 

 buccal cavity. 



One of these subgenera is distinguished from the two others 

 by the flatness of its testa, and by the iipper extremity of the 

 first articulation of its lateral antennae (free in many), not ex- 

 ceeding that of the ocular pedicles. Such are 



Hymenosoma, Leach. 



The testa is triangular or orbicular. {Hymenosoma orhicu- 

 laria, Desm.) 



In the two following subgenera the testa is more or less 

 convex, always triangular, and terminated in front in the man- 

 ner of a bill. The first articulation of the lateral antennae, al- 

 ways fixed, forms a crest, or projecting line, between the 

 fossets of the middle antennae and those of the eyes, and which 

 is prolonged beyond the end of the ocular pedicles. 



Inachus, Fah., 

 Have six segments in the tail ; all the tarsi almost straight, or 



