96 ORTMANN — AFFINITIES OF CAMBARUS. [April i 3> 



[It is very remarkable, that burrowing crayfishes of the southern 

 hemisphere (Parastacus defossus Fax. from southern Brazil is at 

 hand) resemble the North American burrowing species in a remark- 

 able degree externally, chiefly so in the shape of carapace, rostrum, 

 chel?e, length of abdomen, etc.] 



The Chela are very variable in shape : they are fully developed 

 only in old males, but generally quite characteristic for the species. 

 One and the same type is often common to large groups of species, 

 and thus they are often a good help in the investigation of the 

 natural affinities. But in other cases a similar form of chelae is 

 found in different groups which is most striking again in the bur- 

 rowing species. 



Among the more primitive species the shape of the chelae seems 

 to be more or less subcylindrical, and rather elongated. This 

 shape is found in Faxon's first, second, third, and fifth groups, but 

 only in the first, second and fifth it is frequent. Removing C. 

 pellucidus to the fourth group, also in the latter this type of chela? 

 is represented. In part of the second group, and in the third and 

 fourth, a more or less ovate, broad, and depressed chela becomes 

 common, but there is not much uniformity in detail, each group 

 generally developing its own type. 



The above are the more important characters. We see that all 

 of them must be dealt with cautiously, if they are to be used for 

 the investigation of affinities of species. Indeed, in many cases, 

 they support the conclusions arrived at by the examination of the 

 the sexual organs, but very frequently similarities of the above 

 characters are due to convergency. The same is true of all other 

 characters, such as armature of carapace, chelae, shape of "epistoma, 

 antennal scales, of abdomen, telson, etc. 



SUBGENERA OF CAMBARUS, ACCORDING TO THE CHIEF TYPES OF THE 

 SEXUAL ORGANS OF MALE. 



There are three chief types of the male sexual organs (first pair 

 of abdominal appendages), the last of which is easily divided into 

 two subtypes. According to these, I should like to distinguish 

 four subgenera, as follows : 

 i. Subgenus: Cambarus (sens, strict.). 



Sexual organs of male stout, more or less straight, and compara- 

 tively short, truncated or blunt at the tip, the outer part ending in i-j 



