FRESH-WATER BIOLOGY 



Male with hooks on the third and fourth peraeopods. Chelae elon- 

 gated. . . . Section of Cambarus blandingi Harlan 1830. 



About seventeen species, falling into four groups, distributed over the Atlantic 

 and Gulf coastal plain, and passing up the Mississippi valley into the interior basin. 

 C. blandingi (Harlan) is the type species of this group and of the whole genus. Its 

 distribution covers practically all of the range of the section. The other species are 

 more local, and some of them are probably mere local races. The blind species, 

 C. acherontis Loennberg, from Florida, belongs here. 



Species of lakes, ponds, or sluggish rivers, avoiding strong current. 



FIG. 1315. Cambarus (Cambarus) blandingi Harlan. Copulatory organ of male. 

 (After Faxon.) 



X4- 



In other species, the horny tips of these organs are more or less different, and 

 furnish important specific characters. 



43 (38) Second and third peraeopods of the male with hooks on the ischiopo- 

 dite. Sexual organs of male with one soft, and two horny, 

 elongated points Subgenus Cambarellus Ortmann. 



Only one species is found in the United States: C. shufeldti Faxon, from Louisi- 

 ana; a few more species are known from Mexico. 



This species appears to be geographically isolated from its related forms (in 

 Mexico). 



FIG. 1316. Cambarus (Cambarellus) Shufeldti Faxon. 

 (After Faxon.) 



Copulatory organ of male. X 4. 



44(37) Sexual organs of male with two tips, one soft, the other horny. . . 45 



45 (5) Sexual organs rather slender, the terminal tips more or less elongated, 



straight or gently curved. Ischiopodite of third peraeopods 

 of male with hooks, rarely also that of fourth. 



Subgenus Faxonius Ortmann . . 46 



Distribution: Pre-eminently in the large rivers of the central basin (Mississippi and Ohio, 

 and their tributaries). Very few species have reached the Atlantic drainage system. 



46 (47) Sexual organs of male with the tips free only for a short distance. 



Hooks on third, or on third and fourth, peraeopods. 



Section of Cambarus limosus Rafinesque 1817. 



Five species, of which C. limosus (Rafinesque) (very generally called C. affinis Say, which 

 name, however, is a synonym) is the best known: it is found on the Atlantic side of the Alle- 

 ghenies in rivers, ponds, canals, from New York and Pennsylvania to Virginia. The allied 

 species are found at a great distance from this, in Kentucky, Indiana, and Missouri, and among 

 them is the blind cave-species C. pellucidus (Tellkampf). 



47 (46) Sexual organs of male with the free tips longer. Hooks on third 

 peraeopods only ... 48 



