HIGHER CRUSTACEANS (MALACOSTRACA) 



849 



48 (49) Tips of sexual organs rather straight. 



Section of Cambarus propinquus Girard 1852. 



About ten species belong here, but some of them are mere local races. The 

 most important ones are C. propinquus Girard, and C. rusticus Girard, both found 

 in the larger and smaller rivers of the interior basin. The other forms also belong 

 to these river systems, but extend also into the lower Mississippi drainage, to the 

 Atlantic side in Georgia and South Carolina, and to the Great Lakes and the St. 

 Lawrence system. 



FIG. 1317. Cambarus (Faxonius) rusticus Girard. Copulatory organ of male. X 4. 

 (After Faxon.) 



A species characteristic for the lower Ohio and its tributaries. In other species 

 the copulatory organs are more or less different. 

 > 



49 (48) Tips of sexual organs gently, but distinctly, curved. 



Section of Cambarus mrilis Hagen 1870. 



Twelve species are known, but again some may be only local forms. C. mrilis Hagen pos- 

 sesses a wide range in the rivers of the central basin from Arkansas and Kansas to Canada. 

 A very abundant species is C. immunis Hagen, which prefers stagnant, often temporary, pools 

 of the western prairies. The other species are found chiefly in the lower Mississippi drainage 

 in Mississippi, Arkansas, Kansas, Oklahoma. 



50 (45) Sexual organs rather stout, terminal tips rather short, strongly re- 



curved. Ischiopodite of third peraeopods of male with 



hooks Subgenus Bartonius Ortmann . . 51 



Distribution: Chiefly in and near the Appalachian Mountains, but some species on the 

 coastal plain and the western plateau. 



51(52) Eyes rudimentary. Chelae subelonga ted. Carapace subcylindrical. 

 Section of Cambarus hamulatus Cope and Packard 1881. 

 Three cave species belong here (see p. 837). 



52(51) Eyes present. Chelae subovate. Carapace more or less ovate. . 53 



53 (54) Rostrum with marginal spines. 



Section of Cambarus extraneus Hagen 1870. 



Three species, rather local in Kentucky, Tennessee, Northern Alabama, and Northern 

 Georgia. 



54(53) Rostrum without marginal spines. ..."... . . . .- .. v , . 55 



55 (56) Areola wide, or a little narrower. 



Section of Cambarus bartoni Fabricius 1798. 



About four species, distributed over the Appalachian Mountains, where they live 

 in mountain streams, descending more or less toward the lowlands. The best- 

 known form is C. bartoni (Fabricius) (Figs. 1314 and 1318), which covers the whole 

 range of the section, and has developed a number of more or less well defined local 

 races. 



FIG. 1318. Cambarus (Bartonius) bartoni Fabricius. 

 (After Hagen.) 



Copulatory organ of male. X 



In this subgenus, the shape of this organ is rather uniform in all species, which 

 is in strong contrast to the variability seen in the other subgenera. 



