Notes on North American Crustacea. 207 



each other at base as in that species. X. sexdecem-dentatus 

 has been referred by some to the genus Paraxanthus of Lucas, 

 but we cannot perceive that it is generically distinct from X. 

 flames ; in the front is equally prominent. 



Our species was found at Panama by the Rev. J. Howell ; 

 also abundantly at Cape St. Lucas by Mr. Xantus. The north- 

 ern specimens differ from those of Panama only in their smaller 

 size. 



Xantlio dentictilata, nov. sp. 



Carapax sufficiently broad, naked, very deeply areolated anterior to the 

 transverse furrow, the extra-medial gastric lobules being partially divided. 

 An oblique furrow crosses the postero-lateral slope and margin, arising 

 from the transverse furrow half way between the middle and the lateral 

 extremity. Antero-lateral margin armed with nine small but prominent 

 teeth, the anterior one being situated at a lower level than the others 

 (belonging rather to the sub-hepatic region), and separated from the 

 angle of the orbit by a rather deep sinus. Front quadridentate ; middle 

 teeth much the largest. The lobes between the fissures of the external 

 orbital margins are rather prominent. Prajorbital tooth prominent. 

 Latero-inferior regions granulated. Basal joint of the external antennae 

 rather short, but joining a process from the front. In the chelipeds, the 

 carpus and hand are tuberculated above. Ambulatory feet smooth ; a 

 slight tooth at the superior extremity of the carpus-joint. Length of 

 carapax in a male, 0.31 ; breadth, 0.44 inch. 



From the character of the external antennae this species 

 would probably be more properly arranged in Xanthodes, but 

 the carapax is broad as in the true Xanthos. 



Found at Cape St. Lucas by Mr. Xantus, who has been par- 

 ticularly fortunate in collecting new species of a genus the name 

 of which approximates so closely to his own. 



