MEMOIRS 



OF THE 



CAKNEaiE MUSEUM. 



VOL. II. NO. 10. 



THE CRAWFISHES OF THE STATE OF PENNSYLVANIA. 

 Bv .\knold E. Okt.m.wx, Fii.D. 



I. Introduction. 



Tliu present Memoir is a eontiimation of, and an enlargement upon, the prelimi- 

 nary paper published some time ago in the Annals of tlie Carnegie Museum (Vol. 

 HI, 1905, p. 387 et seq.) under the title "The Crawfishes of Western Pennsyl- 

 vania." The object of these publications is to furnish the student with an account 

 of the crawfish-fauna of the state of Pennssylvania as complete as possible, not only 

 from the morphological and zoogeographical, Imt also from the biological, ecolog- 

 ical, and economic standpoint. It is now believed that it is possible to present an 

 approximately complete report upon this important branch of the fresh-water founa 

 of the state, and in the prosecution of the studies of the author a number of (jues- 

 tions were raised, the solution of which proved to be highly interesting. 



It may be well at the beginning to give an outline of the work done. At the 

 outset the writer resolved to go over the whole state, and to collect specimens in as 

 many different localities as possible. Very soon, however, it was discovered that 

 the different parts of the state are of unequal interest. Large tracts, located chiefly 

 in the central, northern, and northeastern parts of the state, proved to be rather 

 uninteresting, only one species of crawfish being present in them, while the western, 

 and chiefly the southwestern, and again the southeastern sections offered more 

 variet} . Thus it became necessary to pay more attention to the latter areas. The 

 uninteresting regions were entered only in a few cases, but a good deal of work was 

 done around their edges, in order to trace their limits as accnirately as possilile. 



The location of the writer in Pittsburgh was advantageous, l)eing central within 

 that section of the state which dllintl the greatest number of problems. Most of 



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