HARRIS : CRAYFISHES GENUS CAMBARUS. 57 



pressure of other work, as well as some other considerations, 

 makes me feel that publication at the present time is desirable. 



A few words of explanation of the arrangement of material 

 may be in place here. The purpose of the paper being the pres- 

 entation of data so far secured in easily accessible form, the 

 arrangement is a purely artificial one. For convenience of 

 reference the species are arranged alphabetically. Under each 

 species is given a catalogue of all the localities from which it 

 has been reported. In a catalogue of fresh-water animals pre- 

 pared for ecological work, it is evidently better to have the 

 material reported from streams rather than from cities, and I 

 have given, so far as I have been able to determine from maps, 

 the stream to which each lot of material probably belongs, 

 or which drains the territory from which it was taken. This 

 may seem to some an addition of little importance, since so far 

 as the range of distribution of a species in a broad way is not 

 affected by its occurrence in Nelson's creek or Big river, so long 

 as it is known that it was taken near Pineville, in the eastern 

 part of the state, but those who are acquainted with the aims 

 of some phases of ecological work will fully appreciate the de- 

 sirability of obtaining all bits of data, even though small and 

 unsatisfactory. For the mere purpose of determining the drain- 

 age systems in which each species occurs, it has been necessary 

 to go over the localities carefully, and it has been thought best 

 to record the decision in each case. As a matter of convenience, 

 the county has also been added when possible, all supplied ma- 

 terial being enclosed in brackets. The states are arranged al- 

 phabetically and numbered, and under them the localities are 

 numbered, so that cross-reference is made convenient. (C. 

 diogenes 15.1 referring to the first locality for C. diogenes given 

 under Kansas.) 



Following the catalogue of localities is given a review of the 

 material of an ecological nature which has appeared on the 

 species under consideration. By means of summaries and tables 

 at the end, it is the intention to bring together and compare 

 points of similarity and dissimilarity in the different species. 

 That the purely artificial arrangement is open to criticism I am 

 fully aware, but it seems to me the best in a paper the object 

 of which is merely the arrangement of data in convenient form 



