2 ORTMANN 
tinguish this subgenus at once from all other Camébarz.' 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 Cambarus.’? 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. 
6. 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....... ANIL eS Ss Paracambarus. 
64. Both tips of male organs soft, with accessory horny spines on 
one of them. Female without spine onsternum 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. 
Camébarus. 
aa. Outer and inner part of male sexual organs distinctly separated 
for a more or less considerable distance at the tips; outer part, 
inthe 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: peretopods..). hn) ee eee eee Cambarellus. 
dd. Outer part of male organs formed by one single horny spine; 
1 Except Cambarus montezume (subgenus Cambarellus). 
2 See Proc. Amer. Philos. Soc., XLIV, 1905, 96 and 97, and Ann. Carnegie 
Mus., III, 1905, 437. 
