No. 2.] STRUCTURE OF TWO FISH TAPEWORMS. 339 



only seven have supposedly been accurately determined, and 

 this paper makes evident grave mistakes in the description of 

 one of these forms. As an example of inaccuracy should be 

 cited the reference by both Kraemer ('92) and von Linstow ('78) 

 to a description of T. toridosa in a work of van Beneden('6i). 

 As a matter of fact, the form described is not even given by 

 the author as torulosa, but as porulosa, and from the figures 

 could not possibly be toridosa. Until all doubtful species are 

 further investigated, no satisfactory synopsis of the entire genus 

 can be made. 



Proteocephalus amb lop litis (Leidy). 



The specimens of this cestode which came into my posses- 

 sion proved to be different in internal morphology from any 

 carefully described species of Proteocephalus, and were at first 

 believed to represent a new species. In reviewing the litera- 

 ture on fish cestodes, I noticed an account by Leidy ('87) of 

 the discovery of a cestode in a rock bass, Atnbloplitis rupestris, 

 which he named Taenia avibloplitis. His description was lim- 

 ited to a few external measurements which did not agree with 

 the dimensions of my specimens. He also stated, however, 

 that the cestode closely resembled Taenia ocellata Rud. Dr. 

 Ward, through the kindness of Dr. Hassell, acting curator of 

 the Helminthological Collection of the United States National 

 Museum, obtained for me Leidy's type specimens. An accurate 

 study of one of these by the section method showed that in 

 spite of certain external differences this species was identical 

 with my specimens. This is simply another illustration of the 

 worthlessness of a description dealing merely with external fea- 

 tures and external measurements in the determination of the 

 species of cestodes. Exclusive of external form and measure- 

 ments, the only difference shown by a careful anatomical and 

 histological comparison of Leidy's specimens with my own was 

 the presence of a greater number of calcareous bodies in the 

 parenchyma and the smaller size of the sphincter muscle. This 

 latter particular was not important because the younger anterior 

 proglottids in my specimens showed the same condition. This 



