2 ORTMANN 



tinguish this subgenus at once from all other Cambari} The 

 male copulatory organs are also different from those of any- 

 other species of the genus, but they approach, to a certain de- 

 gree, those of the subgenera Procambarus and Cambarus. 



This is the sixth subgenus distinguished by the writer within 

 the genus Cambartis. 2 It may be well to point out here the 

 most important characters of these six subgenera by arranging 

 them into a key. 



KEY FOR THE SUBGENERA OF CAMBARUS. 



a. Outer and inner part of male sexual organs in close apposition up 

 to their tips ; tips in the male of the first form horny or soft, 

 with accessory horny spines. 

 b. Both tips of male organs horny; inner part with a strong acces- 

 sory spine on posterior margin. Female with a spine on 

 sternum between fifth pereiopods. Male with hooks on ischi- 



opodite of fourth pereiopods Paracantbarus. 



bb. Both tips of male organs soft, with accessory horny spines on 



one of them. Female without spine on sternum between fifth 



pereiopods. Male with hooks on ischiopodite of third, or of 



third and fourth pereiopods. 



c. Male organs with a small accessory spine, belonging to the 



inner part ; anterior margin with a shoulder near the tips ; 



male with hooks on third pereiopods Procambarus. 



cc. Male organs with one to three horny accessory spines (often 

 tuberculiform or plate-like), belonging to the outer part; 

 shoulder generally absent, if present, remote from the tips ; 

 male with hooks on third, or on third and fourth pereiopods. 



Cambarus. 



aa. Outer and inner part of male sexual organs distinctly separated 



for a more or less considerable distance at the tips; outer part, 



in the male of the first form, entirely transformed into a horny 



spine, rarely with a soft secondary spine. 



d. Outer part of male organs consisting of two rather long spines, 



one horny, the other soft, bristle-like ; male with hooks on 



second and third pereiopods Cambarellus. 



dd. Outer part of male organs formed by one single horny spine; 



1 Except Cambarus montezuma; (subgenus Cambarellus). 



2 See Proc. Amer. Philos. Soc, XLIV, 1905, 96 and 97, and Ann. Carnegie 

 Mus., III. 1905, 437. 



