No. 441.] HABITS OF CAMBARUS. 603 



investigation the same seems to be true of the number of species 

 found in a given stream ; a river with a heavy fall having a larger 

 number of species than one with the same or greater length, but 

 having a more limited vertical range. It is apparent that the 

 former would present much more diverse life conditions than 

 the latter. 



The habits of certain of the North American species of cray- 

 fishes have attracted considerable attention. These are the 

 burrowing species. As burrowing species are to be designated 

 only those forms which show an especial dependence upon this 

 method of life, since it is reasonable to suppose that most, if not 

 all the stream-inhabiting species dig short burrows in the banks 

 at least in certain localities. The species which seem to be most 

 dependent on this habit are C. diogenes, C. gracilis, C. carolinus, 

 C. argillicola, C. simulans and C. immttnis. 



C. diogenes has well been characterized as preeminently a 

 burrowing species. Its presence is usually indicated in the low 

 places where it is most frequently found by the large number of 

 mud " chimneys," about a foot in height, sometimes scattered 

 over several acres, radiating from some sluggish stream, ditch, 

 brook or lower, moister portion of the area, the animals being 

 frequently found at a considerable distance from any permanent 

 body of water. Of the other species C. gracilis seems to be as 

 typically a burrowing species as C. diogenes, and is generally 

 reported as an inhabitant of prairie regions. Adults are to be 

 found in open ponds only in the early spring, and the burrows 

 are often found at long distance from any permanent body of 

 water. C. si ma fans has been reported from streams and ponds 

 and from burrows in a slough. C. hnmunis is known principally 

 from stagnant ponds, resorting to burrowing upon the drying up 

 of the ponds and upon the approach of winter. Of C. argillicola 

 and C. carolinus the nature of the habitat has not been described. 



All of the above are known to be "chimney-building" species. 

 The "chimney," very aptly so called, is a mound of mud of a 

 quite regular, conical or pyramidal form constructed at the 

 mouth of the burrow, with a smooth, internal opening which is 

 merely a continuation of the shaft of the burrow, and is some- 

 times sealed at the top. The chimneys of all the species have 



