52 KANSAS UNIVERSITY SCIENCE BULLETIN. 



on the smallest amount of data, and this is certainly deserving 

 of criticism, but at the present time there need be offered no 

 excuse for the publication or correlation of data of an ecolog- 

 ical character, and little doubt that eventually, if they be care- 

 fully made, the observations will be of importance in the 

 decision of really fundamental questions. 



The paper embodied in the following pages has been sent to 

 the press only after considerable hesitation, and since in some 

 respects it is essentially different from the usual type of sci- 

 entific publication, a few words of explanation, though not of 

 apology, seem to be quite in place. 



In the fall of 1898, at the suggestion of Prof. C. E. McClung, 

 of the department of zoology, University of Kansas, I began 

 studying the crayfishes to be found in the region around the 

 University, and such material as I could obtain from other 

 parts of the state. Being much interested in vegetable ecology 

 at the time, I naturally was interested in the ecological phase 

 of the new work. The most of my own observations have been 

 published, but over two years ago I began to feel the impor- 

 tance of bringing together for a comparative study all that is 

 known of the habits of the North American forms, and work was 

 immediately begun by going through the literature and making 

 abstracts of all parts of a biological nature. More recently I 

 decided that the distribution of all the species should be pre- 

 sented in the same paper. The data are very meager and un- 

 satisfactory, and I fully appreciate the fact that the necessary 

 field-work has been only begun, and if it seemed possible for me 

 to do further field-work I would not publish at the present time ; 

 but there seems little immediate hope of my being able to carry 

 on the work in the way I would desire, and so it is deemed ad- 

 visable to present the material brought together in as convenient 

 a form as possible, in the hope that it may be of use to others 

 more favorably situated for field observations, and perhaps serve 

 as a nucleus or a suggestion for a much more extensive and valu- 

 able piece of biological work on this or some other genus. 



In explanation of the purpose of portions of the paper, it seems 

 desirable to mention in the briefest way some of the work 

 which has been done on distribution in its more limited sense. 



In 1850 Agassiz^ noticed that there is a difference between 



1, Agassiz, L. Lake Superior. Boston, 1850. 



