HARRIS : CRAYFISHES GENUS CAMBARUS. 159 



mals it is hardly safe to suggest.-^ Range in altitude as well as 

 in longitude and latitude is to be noticed. Compare the ele- 

 vation of Boulder, Colo., with lower Louisiana. 



The swamp, stagnant-water and lowland species are many, 

 and it is from these that burrowing species may for the most 

 part be supposed to have originated . Without attempting to pre- 

 sent a list, attention may be called to the forms found along the 

 Atlantic coast plain and the lower parts of the Gulf States — 

 Florida, Georgia, Alabama, Mississippi, Louisiana, and lower 

 Texas. It is very evident, however, that height above the sea 

 is not the only factor determining lowland conditions, and 

 an examination of the streams and species of the Mississippi 

 valley gives some interesting suggestions. 



Data are entirely too meager to say what forms are character- 

 istic of the larger streams. In most of the material reported, 

 data which would make it of value for any such work as this are 

 absent, and very little can be safely concluded from the general 

 locations given. The small tributaries of a stream may be 

 entirely different from the main stream and the species found 

 in them quite different. Until adequate data are secured by col- 

 lectors and published with catalogues of species little is to be 

 hoped for. 



Some species seem to be characteristic of mountain streams, 

 and a comparison of the fauna of the upper Appalachian tribu- 

 taries of some of the Atlantic and Gulf rivers offers suggestions 

 of interest. C. extraneus, C. spinosus, C. bartonii, C. acuminatus, 

 C. erichsonianus, C. forceps, C. longulus, and perhaps several 

 others, seem to be confined to mountain streams. 



That the number of species bears no relation to the area 

 drained by the river is well known, and may be illustrated by 

 the following table : 



Penobscot, 9000 miles, one species. ^^ 



Hudson, 13,400 miles, two species. 



Potomac, 14,500 miles, seven species. 



Cape Fear, 8,400 miles, three species. 



Santee, 14,700 miles, six species. 



Tennessee, 43,900 miles, twenty-one species. 



25. The burrowing species are not so easily collected as are some of the others, and our 

 knowledge of their actual distribution is very imperfect. 



26. In comparing the number of species found in different streams or states I have counted 

 varieties as species. 



