No. 396.] MWORTH-AMERICAN INVERTEBRATES. 961 
Cambarus.— Last thoracic segment without a gill, thus 
reducing the number in each branchial chamber to seventeen. 
Orifice of green gland at apex of tubercle. First abdominal 
appendages of males bifid and hooked or toothed at the apex. 
One or more pairs of thoracic legs of males with a hook-like 
tubercle on the third segment. In the females, annulus ven- 
tralis developed as a depressed cone on the sternum between 
the bases of the last pairs of legs. 
1 Eyes normally Smee š ; ; $ i ; i ea 
1 Eyes atrophied i ; ; i ; , . 84 
2 Areola very narrow or obita : ; | í : k og 
2 Areola of moderate or excessive width . s 7 i ‘ 15 
3 Rostrum with lateral spines . : , i ; ‘ i ae 
3 Rostrum without lateral spines ; : at 
4 Rostrum excessively lengthened, the postetior sonics af carapace one- 
third as long as anterior . : . C. lanctfer Hag. 
4 Rostrum not excessively kaioek ES portion of carapace more 
than one-third as long as anterior 5 
5 Rostrum with a low median Papmone.! carina TE Aidi F ax. 
5 Rostrum without a carina i 
6 Sides of carapace coarsely adat: S inner aa of chelæ aii el 
sinuate ; ; ; ot 
Sides of carapace slightly rannat or s ; ; : e, 
Areola obliterated for at least a portion of its length ; ‘ 38 
Areola not obliterated at any point . 
First abdominal appendages of males Py ake ndr straight, 
acute tips. Annulus ventralis of females with a pronounced central 
fossa . C. palmeri longimanus Fax. 
First abdominal setehdanes of = with short recurved tips. Annu- 
lus ventralis of females with the central fossa almost obliterated 
C. difficilis Fax. 
9 Lateral teeth of rostrum small ; i } ‘ | CO, aes Fax. 
9 Lateral teeth of rostrum stron . - . Io 
10o Anterior border of carapace dapulated bijo the eye 
C. longidigitus Fax. 
ONNA 
oo 
10 Anterior border of carapace not angulated. : C. pilosus Hay 
11 Base of rostrum not foveolate . ý C. advena LeC. 
11 Base of rostrum with a more or less acad a. ; ae 
12 Anterior border of carapace angulated below the eye . ‘ ae 5 
12 Anterior border of carapace not angulated below the eye : I5 
13 Areola linear but not obliterated . i > + E praci W 
13 Areola obliterated in the middle . . ane ; . 14 
14 Sides of rostrum straight , ‘ : ; . C. diogenes Gir. 
