i 9 o S .] ORTM ANN— AFFINITIES OF CAMBARUS. 97 



horny teeth, which are sometimes recurved, or compressed, or plate- 

 like, and are always sharply distinguishable from the blunt end. 

 Inner part terminated by a shorter or longer, acute spine, which is 

 sometimes distinct from the tip of this part, so that it appears two- 

 pointed. In the male the third or the third and fourth pereiopods 

 have hooks. 



2. Subgenus : Cambarellus nov. subgen. 



Sexual organs of male stout, straight, or slightly curved at the 

 tips. Outer part ending in two horny teeth, which are rather long, 

 taper rapidly, and are not sharply distinguishable from the end, 

 which is not truncated. Inner part terminated by a rather long, 

 acute spine. In the male, the second and third pereiopods have 

 hooks. 



[The two following subgenera represent the third type of male 

 sexual organs, in which both parts, outer and inner, each terminate 

 in only one tooth, which is rather slender, and not sharply distin- 

 guishable from the end, which is never truncated.] 



3. Subgenus : Faxonius nov. subgen. 



Sexual organs of male shorter or longer, not very stout, generally 

 slender, or with slightly curved tips. Tips never truncated, ending 

 always in two more or less elongated spines, the one formed by the 

 outer part, and horny, the other formed by the inner part and 

 softer. There is never more than one tip to the outer part, and there 

 is no terminal tooth distinguishable, but the tip tapers gradually, 

 or the whole outer part is setiform. In the male generally the third 

 pereiopods only have hooks, very rarely (in C. pellucidus') hooks 

 are found on third and fourth pereipods. 



4. Subgenus : Bartonius nov. subgen. 



Sexual organs of male very uniform throughout the subgenus. 

 They are short and thick, inner and outer part each terminating in 

 only one short and thick spine, tapering to a point. Both terminal 

 spines are strongly recurved, forming with the basal part about a 

 right angle. In the male, only the third pereiopods possess hooks. 



Subgenus : Cambarus. (Type : C. blandingi. ) 



This subgenus comprises Faxon's first and second group, exclud- 

 ing the species C. pellucidus. Both groups are rather heterogeneous, 

 and so is this subgenus, and there are considerable variations in the 

 male sexual organs. The chief feature of the latter is their blunt 



