astacid^:. 105 



tonii from North America. The habitat is uncertain, and so not of de- 

 cisive value* 



Concerning the geographical distribution of the genus Cambarus, we 

 find the interesting fact that the most distinct group, containing the 

 species related to C. acuhis, seems to be confined to a limited territory. 

 Its boundaries answer for the most part to the Southern fauna, traced 

 by Professor L. Agassiz for the Chclonians, but is somewhat more exten- 

 sive, as some species are observed to live also in the upper parts of the 

 rivers and their affluents. Beginning on the Atlantic coast in Virginia 

 (also farther north, as with the Chclonians), it extends through the Caro- 

 linas, Georgia, Florida, Alabama, Mississippi, Louisiana, and Texas. 



Some species follow up the Mississippi and its tributaries for a great 

 distance, while a peculiar variety, described by me as C. acidm var. A, 

 has its habitat far to the north, and is not to be found in the southern 

 parts. It is very interesting to remark that the same species is to be 

 found farther north on the Atlantic coast, forming also a peculiar va- 

 riety, described by me as C. acutus var. B, from New Jersey and New 

 York. It was impossible for me to give an adequate account of it, as 

 I have not seen the male. 



Our knowledge of the Mexican fauna is very meagre, but it seems 

 probable that a few species at least belong to the same group. Still 

 more interesting is the fact that some species of the other Cambarus 

 groups, living within the limits noticed for the species for the first 

 group, have an analogous appearance and shape of body, viz., C. lancifer, 

 C. immunis, C. extraneus, C. advena, and C. Carolinus. 



I have heretofore stated that these species, even when viewed under 

 other relations, constitute aberrant forms. But it should be remem- 

 bered that several species, viz., C. placidus, C. obesus, C lafimanus, which 

 also live in the same southern country, belong in all their characters 

 to very different groups. The groups of Cambarus, as defined by me, 

 do not apparently coincide with certain faunal regions. 



The species of the second group, except the aberrant forms before 

 mentioned, especially the species related to C virilis, belong to the 

 northern and middle parts of North America. These species occur es- 

 pecially in the Northern Lakes and their affluents, also in the Missouri, 

 Mississippi, Ohio, and their tributaries, and in Texas. 



C. ajjinis, a somewhat peculiar species, alone lives in the rivers run- 

 ning eastward to the Atlantic coast, in the Hudson, Delaware, Potomac, 

 Suscpiehanna, and their affluents. 



* Von Martens, in Troschel Archiv, 1869, T. 35, p. 15 sqq., describes two species of fresh- 

 water crabs from Brazil, Aslacus pilimanus, p. 15, Tab. 2, fig. 1, from Porto Allegro and Santa Cruz, 

 in the affluents of the Rio Pardo River, which is an affluent of the Jacuhy River, with burrowing 

 habits, Astacus Brasiliensis, p. 16, Tab. 2, fig. 2, from Porto Alegre and from Roedersberg, in 

 ponds and small rivers. The latter is perhaps the species from Brazil mentioned by me, p. 11. 



Professor H. Burmeister writes to me that he has seen a species of Astacus from the Banda 

 oriental. 



14 



