160 



CORYSTIDJR. 



rounding the cardiac and genital regions, and another short 

 transverse depression over the intestinal region, forming 

 altogether, in many specimens, a remarkable similitude to 

 the features of the human face ; from which circumstance 

 T have given it the English name of " the Masked Crab.'" 1 

 There are three acute teeth on each side of the carapace, 

 the first forming the external angle of the orbit ; the second 

 placed on the margin of the hepatic, and the third, which 

 is very small, on the margin of the branchial region : the 

 surface is covered with minute scattered tufts of very short 

 hair, scarcely distinguishable by the naked eye. The 

 rostrum is deeply notched. The orbits are minutely granu- 

 lated on the margin. The external antennoe are very long, 

 setaceous and doubly ciliated throughout their whole 

 length, as are also the pedipalps. The anterior feet in the 

 male are twice as long as the body; the arm nearly cylindrical, 

 and nearly the same length as the arm ; the wrist about 

 half as long and furnished with two spines on the inner 

 side ; the hand gradually enlarging forwards ; the fingers 

 considerably inflected, and ciliated. In the female these 

 feet are not longer than the body ; the hand scarcely 

 longer than the wrist, and somewhat gibbous. The re- 

 maining pairs of legs are compressed, and doubly ciliated. 

 The abdomen in the male is five-jointed ; the third becom- 

 ing abruptly narrower than the second ; and the terminal 

 one obtuse and rounded. In the female the first two joints 

 are very broad ; the third abruptly narrower, and, with the 

 remaining joints, forming an oval : in both sexes this part 

 is marginated with rather long hair. 



The colour is pale red, passing into yellowish white ; the 

 arms rather deeper red. In the female the colours are 

 much less bright and clear than in the male. 



The sexes of this species differ so much from each other, 





