INTRODUCTION. I I 



tributary to Lake Erie. The species is evidently not, as believed 

 by McCormick, ' ' restricted to a very narrow geographical range." 

 The cysts formed by this parasite reproducing in the subcutan- 

 eous tissue may reach a diameter of one-third inch, and as many 

 as eleven cysts have been noted on a single fish. It would seem 

 that in some cases they must inevitably cause the death of the 

 host. 



Specimens of all the species of fishes recorded by Kellicott, 

 Williamson, Parker and the writer are deposited in the museum 

 of the Ohio State University. 



In the preparation of this paper free use has been made of 

 the works of the various writers on Ohio fishes, of " The Fishes 

 of North and Middle America" (Bulletin 47, U. S. National 

 Museum), by Drs. David Starr Jordan and Barton W. Evermann ; 

 of Dr. O. P. Hay's "Lampreys and Fishes of Indiana" (19th 

 Annual Geol. Rept. of Ind. ), and of the reports and bulletins of 

 the U. S. Commission of Fish and Fisheries. The classification 

 is that adopted by Jordan and Evermann in Bulletin 47, U. S. 

 Natl. Mus. The ke}^s for the separation of families, genera and 

 species have, for the most part, been taken from the same work, 

 but modified and abridged to meet the requirements of the more 

 limited scope of this paper. The descriptions have been drawn 

 largefy from the same source, but as far as possible these have 

 been verified for Ohio specimens, and modified as occasion 

 demanded to make them apply more closely to the species as 

 found in Ohio. 



While it is not the purpose to discuss in this paper the gen- 

 eral anatomy of the fish, such as may be found in any good 

 laboratory guide on zoology, a few hints to the beginner in 

 regard to methods of procedure and to some particular points of- 

 structure may here find a place. The teeth in some species are 

 borne on nearly all parts of the mouth and pharynx— -premaxil- 

 laries, maxillaries, mandibles, vomer, palatines, tongue, hyoid 

 apparatus, pterygoids and pharyngeals, but may be wanting from 

 any or all of them. The examination of all but the last men- 

 tioned can usually be satisfactorily made through the open mouth 

 -by using a blunt dissecting needle or the head of a pin as a 

 '"feeler." It is the determination of the number and arrange- 



