STALK-EYED CRUSTACEA 201 



sometimes transverse ; their fossae may communicate with 

 the orbits, or may be circumscribed, then they are very 

 narrow from before backwards. The external antenna are 

 very short ; their basal joint is often wider than long, and 

 their terminal joints, which are sometimes rudimentary, 

 occupy usually the hiatus of the internal orbital angle. 



The epistome is usually linear. The buccal cavity is 

 usually quadrilateral, and is never advanced to a level 

 with the insertion of the eye ; it may be slightly contracted 

 in front, and its anterior border may be a little bowed. 

 The fifth joint of the external maxillipedes articulates 

 with the fourth at the middle of its anterior border or at 

 its internal or external angle, or may be completely hid 

 behind it. The external appendage (exognath) is usually 

 styliform, or may be rudimentary. The sternal plastron is 

 almost always wider than long, and contracted anteriorly. 



Range. — Fresh and salt water of warm and tropical 

 regions, and damp and dry lands of most tropical and 

 subtropical countries. 



Family I. Thelphusidae 



Family II. Geocarcinidae. 



Family III. Ocypodidae. 



Family IV. Grapsidae. 



Family V. Pinnotheridae. 



Synopsis of the Families. 



a. The fifth joint of the external maxillipedes joins 

 the fourth at its external angle, or at the centre of its 

 anterior border. The fourth joint is broad, with rounded 

 anterior margin, or triangular. 



The carapace is transversely oval or rounded. — 

 ( Thelphusid(£. ) 



