417 Annals of the Carnegie Museum. 



The fine point on the tip of the outer part of the copulatory organ 

 in C. atkinsoni is a special feature of this species, which has not been 

 observed in any of the other species of the subgenus Procambarus, but 

 in specimens of C. cubensis before me I see in its place a slight and 

 insignificant swelling. 



C. digueti Bouvier, from western Mexico, which is also a Pro- 

 cambarus, is morphologically too remote from all these species, so 

 that we do not need to compare it in detail. 



Including this new species, the subgenus Procambarus consists now 

 of the following six species: C. digueti Bouvier (western Mexico), 

 C. williamsoni Ortmann (Guatemala), C. pilosimanus Ortmann 

 (Guatemala and British Honduras), C. mexicanus Erichson (eastern 

 Mexico), C. atkinsoni Ortmann (Isle of Pines), C. cubensis Erichson 

 (Cuba). Of these, however, C. williamsoni and pilosimanus are very 

 closely allied, and may possibly be on y forms of the same species. 



