ASTACID.E. 105 



toiiil from North America. The lialjitat Ls uncertain, and so not of de- 

 cisive value.* 



Concerning the geographical distrihution of the genus Camhanis, Ave 

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

 species related to C. acutus, seems to he confined to a Umited territory. 

 Its houndaries answer for tlie most part to the Soutliern fiiuua, traced 

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

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

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

 (also farther north, as with the Chcloiiiuiis), 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. acutus 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. acutns var. B, from New Jersey and Nevv^ 

 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 sjiecies of the other Camharus 

 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. advcna, 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., 0. pluddus, C. obesvs, C. latimanus, which 

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

 to ver^' different groups. The groups of Caiiibarus, as defined by me, 

 do not apparently coincide with certain fiiunal regions. 



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

 mentioned, especially the sj^ecies related to C. viriUs, 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. uffiuis, a somewhat peculiar species, alone lives in the rivers run- 

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

 Susquehanna, and their affluents. 



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

 water crabs fi-om Brazil, Astacus pilimanua, p. 15, Tab. 2, fig. 1, from Porto AUegrc and Santa Cruz, 

 in tlie affluents of tlie Rio Pardo Kiver, wliicli is an affluent of tlie Jaeuhy River, witli burrowing 

 habits, Aslacus BraxUiensh, p. 16, Tab. 2, fi». 2, from Porto Alegre and from Roedersljerg, in 

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



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

 oriental. 



14 



