178 A REVISION OF THE ASTACnm 



that the genus Cambarus once flourished in the rivers of Europe. (See pages 42, 176.) 

 The cave species of the United States belong to the same genus as those inhabiting the 

 outside waters, but are not closely related to any of them. They may be considered as 

 derived from an ancient outside fauna of that region. (See page 42.) 



VI. The genus Cambarus ranges from Lake "Winnipeg to Cuba and Guatemala, 

 from New Brunswick to Wyoming Territory (in Mexico to the Pacific Ocean). Like the 

 Unionidae of the same waters, the Cambari are wonderfully rich in species, the evolution 

 of specific forms having gone on much more rapidly here than in the regions inhabited by 

 their relatives, the Astaci. Within the limits of the United States west of the Rocky 

 Mountains, and in Mexico and Cuba, fifty-two species of Cambarus are known, while the 

 described Astaci (including the subgenus Cambaroides) of Europe, Asia, and the Western 

 United States number but fourteen species, the chances of discovery of new species through 

 further exploration being greatly in favor of the genus Cambarus. 



Witli regard to the distribution of the species of Cambarus, the whole territory occupied 

 by them seems to fall into two provinces ; — a southern province, embracing the Atlantic 

 States south of North Carolina, the Gulf States, Mexico, and Cuba; and a northern prov- 

 ince, which includes the Atlantic States north of South Carolina, the States of the Missis- 

 sippi Valley (in sensu extensd) north of the Gulf States, and Canada. The southern province 

 is characterized by the prevalence of species belonging to Groups I. and II. (ft Blandingii 

 and C. advcna groups). All of the fifteen species of Group I., excepting ft pellucidtis, are 

 found within the limits of this province as defined above. C. pellucidus comes from the 

 caves of Kentucky and Southern Indiana. Five of the six species belonging to Group II. 

 are found in the southern province ; the fifth, ft gracilis, is a northern species (Wisconsin, 

 Iowa, Illinois). C.&imulans has been found in Texas and to the northward in Kansas. 

 The only two species belonging to Group V. (ft Montezumce ami ft Shufeldtii) are confined 

 to the southern province, in Mexico and Louisiana. One species belonging to Group 1., 

 ft Blam/itii/ii, extends northward beyond the limits of the southern province as far as 

 New York along the Atlantic coast, ami up to Wisconsin in the Mississippi Valley. In 

 both the East and the West, the northern form distinctly differs from the southern. (See 

 page 22.) 



Besides the species of Cambari belonging to Groups I., II., and III., there are found 

 within the limits of the southern province six species* belonging to Group III. (ft. />'"/■- 

 tonii group), and nine species f of Group IV. (ft affiuis group). Only eight of them, how- 

 ever, are restricted to the southern province; and of these eight, three (ft Girardianus, 

 Alabamensis, and compressus) are known only from the extreme northwestern corner of 

 Alabama, in the Tennessee River basin, while three (ft acuminatus, latimanus, and Jor- 

 dam chiefly inhabit the upper portions of the river-courses in the mountainous regions 

 of the province. ft exlraneus and ft spinosus are border species with respect to the two 

 provinces, being found in the streams on each side of the Alleghany divide, in South 

 Carolina, Georgia, and Tennessee, ft Dior/cues, immunis, virilis, and rusticus have their 

 populous centres of distribution in the north, although they have extended far southward 

 on certain lines. 



In the uorthern province the species of the third and fourth groups (allies oiGBar- 

 tonii and ft affinis) are the dominant forms, wellnigh to the exclusion of those belong- 

 ing to the firsl and second groups. Nine species belonging to Group III. and eleven to 



* C. acuminatus, C. lalimanui, C, Diogenes, C. extraneus, ('. Girardianus, and CJordani. 



f C. immunis, G \fississippiensis, C. Alabamensis, C. compressus, C.lanci/er, C. virilis, C. rusticus, C.spi- 



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