ASTACIDJE. 75 



Astacus. The foreborder of the eephalothorax is strongly 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 tip 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. Diogenes (united by me 

 with C. Bartonu). 



2. The other group, C. Carolinus and C. advena, differs in having the 

 front border of the eephalothorax not angulated, the very narrow post- 

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

 ilar to those described hi G. acutus. 



Synopsis of the Species. 



1st Section. 

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



A. Areola linear: C. obesug, C. Nebrascensis. 



B. Areola broad : C. Darlonii (with C. pusillus, C. montanus, C. longulus, C. Diogenes), C. 



robustus, C. laiimanus. 

 Incerta? sedis : C. Mexicanus, C. Cubensis. 



2d Section. 



Front border of the eephalothorax straight; first abdominal legs not hooked: C. arh-ena, C. 

 Carolinus. 



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 especially the case in the species united by me with C. Bar- 

 tonii, viz. in O. pusillus, C. montanus, C. longulus, and C. Diogenes. More 

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



24. Cambartjs Bartonu Fabricius. 



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

 Hist. Xat. Crust. T. VI. p 240. — Say, Journ. Acad. N. Se. Philad.. T. I. p. 1G7, 2. — Har- 

 lan, Med. and Pins. Research., p. 230, fig. 3. — Erichson, Archiv. T. XII. p. 9 7, n. 17. — De- 

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



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

 First abdominal legs of the male : 



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



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

 Inner sexual parts of the male : 



first form, fig. 135 ; side, fig. 136. 



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

 Inner sexual parts of the female, fig. 139. 

 Antennal lamina, fig. 160, a ; epistoma, b; spine of the second joint of the exterior antenna, c. 



Mas. Rostro brevi, lato, fere quadrangulari, ante apicem utrinque 



