7] PROTEOCEPHALIDAE — LA RUE 



INTRODUCTION 



Several years ago while studying under Professor Henry B. Ward 

 at the University of Nebraska the writer began an investigation of a 

 <;estode parasitic in Ambly stoma tigrinum (Green). That investigation 

 resulted in a paper (La Rue 1909) in which a number of points in the 

 anatomy of Proteocephalids were cleared up and certain problems were 

 outlined for investigation at an early date. In the meantime the writer 

 became interested in the large number of Proteocephalids which Pro- 

 fessor Ward had secured by work in the field and by exchange. The 

 writer had also made some collections. A preliminary study of the 

 available material by the writer was convincing to Professor Ward that 

 a more complete and comparative study of the group was desirable and 

 that the results of such a study would prove of value to helminthologists, 

 not only of America but also in Europe. Such a study seemed more 

 desirable since but two comparative studies of the group had been made 

 in more than fifteen years, the first by Riggenbach (1896) mostly on the 

 species infesting fish, and the second by Schwarz (1908) wholly on the 

 species infesting snakes and reptiles. The fact that very little had 

 been done on the genus by American investigators furnished an added 

 incentive to undertake the work. 



At Professor Ward's suggestion and under his direction the writer 

 "undertook an investigation of the genus which would be comprehensive 

 in scope and at the same time comparative. For this purpose Professor 

 Ward augmented the material already at hand by securing the loan of 

 alcoholics and prepared slides from several European and American 

 investigators and from the collections of the Smithsonian Institution 

 and the Bureau of Animal Industry at Washington. Unfortunately 

 specimens of certain material could not be secured either because it 

 had been lost or because it could not be removed from the collections. 



The lack of some of this material has caused the writer to change 

 the plan of the paper somewhat. Instead of making a fresh study of 

 each species it has been necessary in describing certain species to depend 

 on the data secured from the literature. These data have been recom- 

 liined and quotations have been made, sometimes quite extended, while 



