STALK-EYED CRUSTACEA 307 



Synopsis of the Genera. 



A. Carapace wider than long. Front not in the form 

 of a rostrum. — (Hepati/s.) 



B. Carapace nearly as long as broad. Front produced 

 into a rostrum. — (Osac/ie/a.) 



I. Hepatus. 



Hepatus . . . Latreille, H. Milne Edwards. 

 Calappa . . . Fabricius. 



Carapace very wide, convex, regularly bowed in front, 

 strongly contracted posteriorly; hepatic regions very large, 

 branchial regions small. Front narrow, straight, very 

 prominent and placed much above the level of the lateral 

 border of the carapace, which is prolonged under the 

 orbits to reach the sides of the buccal cavity. The orbits 

 are small, circular, and placed upon the level with the 

 front. The internal antennae, wide apart, are folded under 

 the front. The external antennae occupy the internal 

 angle of the orbit. Their basal joint is narrow, but very 

 long ; the second joint is small, and the flagellum is 

 almost rudimentary. The buccal cavity, narrow in front, 

 regularly triangular, is advanced to a level with the 

 inferior border of the orbits, and is completely covered 

 by the external maxillipedes, of which the fourth joint 

 is triangular. The ^rst pair of legs strong, without being 

 very large, and can fold themselves exactly against the 

 front of the body and become concealed. The hand has 

 a crest above, and the pincers are slightly inclined down- 

 wards and inwards. The walking legs are of moderate 

 length. 



The abdomen has seven segments. 



Range. — West Indies, warm American Seas. 



