ASTACIDiE. 75 



Astacus. The forebordtn* of the oephalothorax is utrongly angulated. 

 The body, especially the postabdomen and the hands, is broader. The 

 first pair of abdominal legs of the male has a peculiar and striking de- 

 velopment. The tij) of the exterior part forms a larger and more 

 strongly recurved tooth ; the tip of the interior part is broken, short, 

 .and conical. The second pair of legs and the third are ciliated with 

 hairs. Burrowing habits are observed in C. Dior/cncs (united by me 

 with C. Bi(rto)iii). 



2. The other group, C. CaroUmis and C. advcna, differs in having the 

 front border of the oephalothorax not angulated, the very narrow postr 

 abdomen, and principally in the form of the first abdominal legs, sim- 

 ilar to those described in C. acufiis. 



Synopsis of the Species. 



1st Section. 

 Front border of the ccphalotliorax .angulated ; first abdominal legs strongly hooked. 



A. Areola linear: C. obcsu.i, C. Kebrasccnsis. 



B. Areola broad : C Barlonii (with C. pusillus, C. 7nontanus, C. loiir/ulus, C. Diogenes'), C. 



robuslus, C. latimanu.i. 

 InccrtiB sedis : C. Mexicanus, C. Cuhensis. 



2d Section. 



Front border of the cephalothorax straight; first abdominal legs not hooked: C. adoena, C. 

 Carolinua. 



The determination of the species in this group is not so certain as 

 in the foregoing groups. In some species the entire lack of typical 

 specimens, or the insufficiency of materials, has perhaps misled me 

 and occasioned errors. 



This is es^DCcially the case in the species imited by me with C. Bar- 

 tonii, viz. in C. pusillus, C. montanus, C. lougidus, and C. Diogenes. More 

 ample material will either confirm my views or correct my errors. 



24. Cambarus Bartonii Fahidus. 



Astacus Bartomi Fabr., Supplem. Ent., p. 407, n. 3. — Bosc., Hist. Nat. Crust., T. II. p. 40. — Latr., 

 Hist. Xat. Crust, T. VI. p 240. — Say, Journ. Acad. N. Se. Philad., T. I. p. 167, 2. — Har- 

 lan, Med. and Phys. Research., p. 230, fig. 3. — Erichson, Arcliiv. T. XII. p. 97, n. 17. — De- 

 Kay, X. Y. Zoology, VI. 22, PI. 8, fig. 25. 



Figures on PI. I., II., and III. 

 First abdominal legs of the male : 



first form, tig. 47 in front; fig. 48 outside. 



second form, fig. 49 in front ; fig. 50 outside. 

 Inner sexual parts of the male : 



first form, fig. 135; side, fig. 13G. 



second form, fig. 137; side, fig. 138. 

 Inner sexu.al parts of the female, fig. 139. 

 Antennal lamina, fig. 166, a; epistoma, ft; spine of the second joint of the exterior antenna, c. 



Mas. Rosti'o brevi, lato, fere quadrangulari, ante apicem utrinque 



