DISTEIBUTION OF OEAY-FISHES. 813 



in both the Lobster and the Cray-fish. In the latter animals each of these gills forms a simple 

 stem ending above in a plume and plate; in the former this "stem is, as it were, completely split 

 into two parts longitudinally, one half corresponding with the lamina (plate) of the Cray-fish gill, 

 and the other with its plume." 



The shedding and the spawning habits of the Cray-fish correspond very closely with those 

 of the Lobster, in connection with the description of which animal the subject has been discussed 

 at some length. 



As stated above, the American Cray-fishes belong to two genera, Astacus and Cambarus, while 

 all the European species belong to the one genus Astacus. The only marked difference between 

 the two genera is this, that while in Astacus there are eighteen gills on each side, in Cambarus 

 there are'only seventeen. This difference in structure is considered to be of sufficient importance 

 to warrant Jihe formation of the two genera, but the external differences, such as the variation in 

 shape of the body, and in the proportionate sizes of the several external parts, which are more 

 apparent and more striking to the superficial observer, have only specific value. On such 

 differences as these are founded the thirty-two species of Cambarus and the six species of Astacus, 

 belonging to the North American fauna. More careful and detailed studies of large collections 

 of Cray-fishes from different parts of North America may serve to greatly reduce this number of 

 species, and if such should follow, it would simply go to prove that some of the differences now 

 supposed to be of specific importance are merely varietal. Strangely enough, all of the North 

 American species of Astacus are limited to the western slope of the Sierra Nevada Mountains, 

 that is to say, to that portion of our country most distant from Europe; while the genus Cambarus 

 is confined to the intervening area between the Kocky Mountains and the Atlantic coast. The 

 six species of Astacus are variously distributed through California, Oregon, Washington Territory, 

 and British Columbia, but only one species, A. nig'rescens, appears to be used as food, at least to 

 any extent. This probably results from the fact that this is the only species found in the vicinity 

 of San Francisco, outside of which city there is little or no demand for this sort of food. Adult 

 individuals of this species exceed four inches in length, and when living are blackish in color; 

 after death, however, they become of a light grayish tint. According to Mr. Lockington, of San 

 Francisco, this species is larought to that city only in small quantities, the demand for it being 

 slight. The supply is mostly obtained from Coyote Creek, Santa Clara County, and from the 

 sloughs of the San Joaquin. 



The genus Cambarus is pretty generally distributed throughout the region east of the Eocky 

 Mountains. No Cray-fishes have ever been found, however, in the New England States, excepting 

 in the extreme western parts of Vermont and Massachusetts and in Central Maine, and ten years 

 ago no species had been recorded from most of the Western Territories, especially between the 

 Eocky Mountains and the Sierra Nevada, where if any Cray-fishes should be found in the future it 

 will be interesting to know whether they belong to the western genus, Astacus, or the eastern, 

 Cambarus. 



At present we know so little, comparatively speaking, of the invertebrate fauna of the rivers oi 

 the Territories that it is not at all strange we should have so few records of Cray -fishes from them; 

 but it is very probable that Cray-fishes exist there in greater or less numbers. New England, on 

 the contrary, has been too well explored to leave much doubt but that Cray-fishes are absent from 

 it excepting in the localities above cited. To enter into a discussion of all the species of North 

 American Cambarus would lead us away from the main object of this sketch, which is intended 

 principally to point out the range and habits of those species known to be eaten. Suffice it to 

 say that the species are more or less irregularly distributed, some States, or even sections ot 



