578 Monograph of the 



pairs of ambulatory feet. The intromittent organs reach 

 a little beyond the middle of the penult segment of the 

 abdomen ; they curve outwards strongly near their extrem- 

 ities, and then inward to their tips, which again point a 

 little outward. About the size of the ornatus. 



Pinicate Bay, Gulf of California. Museum of the 

 Smithsonian Institution. 



CALLIXECTES ARCUATUS, nov. sp. 



I have but one specimen of this species, and it is very 

 closely allied to the diacanthiis. The carapax, however, is 

 more evenly convex, and fniely granulated, and the antero- 

 lateral borders are quite semicircular. The sternum is not 

 so flat as in diacanthiis. The abdomen of the male is much 

 broader than in diacanthiis, being nearly as broad as in 

 hastatus, but the penult joint exhibits no constriction near 

 the base, being, on the contrary, wider at the base than 

 anteriorly. The intromittent organs exhibit a striking re- 

 semblance to those of diacanthiis, beinii^ more alike than 

 any other of the known species of the genus. Almost the 

 only difl'crence that can be observed is, that they are, per- 

 haps, more slender in this species. 



The chelipeds are slightly shorter than in diacanthiis, and 

 the costEB of the manus and carpus are very sharply de- 

 fined and closely granulated. The three spines on the 

 mcros are more slender and closer together, and what is 

 quite remarkable, there are three sharp and equal spines 

 on the carpus. It is of about the same size as the ornatus. 



Cape St. Lucas, John Xantus. Museum of the Smith- 

 sonian Institution. 



CALLINKCTES PLEUEITICUS, nov. sp. 



This species in some of its characters closely resembles 

 larvatus, while in others it is allied to arcuatus and diacan- 

 thus, but nevertheless it is distinct from any of them. In 



