MAIOIDEA. 127 



The distance between the angle on under side of penult joint of 

 legs and base of same joint, is about half the distance from the same 

 angle to the apex ; while in the Petiverii, this angle is nearer the apex 

 than the base. 



ACANTHONYX DEBILIS. 



Maris : Petiverii affinis. Carapax paulo convexus, marginibus latera- 

 libus parallel is, regione mediand obsolete bi-tuberculatd, tuber culis 

 setigeris. Pedes antici maris reliquis vix crassiores, digitis parce 

 hiantibus, carpo non cristato. Tarsus pedis postici 1214 spinulis 

 seriatim armatus ; articulus penultimus late triangulatus, infra oblique' 

 truncatus. 



Near Petiverii. Carapax a little convex; lateral margins parallel; 

 stomach region with two setigerous points. Anterior feet but little 

 stouter than the following; fingers slightly gaping, and meeting only 

 at the extremity ; teeth triangular ; carpus not cristate. Tarsus of 

 posterior feet, with twelve to fourteen spinules in a row ; penult 

 joint broad triangular ; truncate margin oblique. 



Plate 5, fig. 5 a, hand of male, enlarged five diameters; b, extre- 

 mity of posterior legs. 



Valparaiso, Chili. 



Length of carapax of male, nine lines; breadth, five and two-thirds 

 lines; distance between first and second lateral teeth, two and one- 

 eighth lines ; distance between second and third lateral teeth, one and 

 one-eighth lines. 



Differs from the Petiverii in the small hands of the males, the teeth 

 of the fingers, the cristate carpus, and the two obsolete tubercles on 

 the stomach region ; from the lunulatus, in the small hands in the 

 males ; from the simplex, in the stomach tubercles, the spinules of the 

 tarsi. The abdomen has only six joints, and not seven, as in the Mac 

 Leayi of Krauss; it has the same shape as in the Petiverii (Plate 5, 

 %. 6). 



