148 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



nym of Icihyotxnia is by following Ijiihe (1899) in considering Pro- 

 teocejyhalus preoccupied, and hence unavailable. Otherwise Ictliyo- 

 tsenia is a synonym of Proteocej)lialus, or the two genera are distinct 

 and valid, with characters fixed by the type species T. JllicoUis and 

 T. amhigua, respectively. Even Liihe (1899), in commenting on T. 

 amhigua as a species inquierenda, has not seriously proposed that 

 two different genera are involved in this question of synonymy. 

 Riggenbach (1896) has listed Idhyotsenia amhigua and /. flicollis 

 among his species of Icthyotsenia. Benedict (1900) bases his pref- 

 erence for Proteocefhalus on this action of Riggenbach's. Larue 

 (1909) notes that Liihe has given certain reasons for retaining 

 Icthyotsenia, but he uses Proteocephalus on the grounds of priority 

 without further discussion. 



Liihe (1899) has objected to the generic name Proteoceplialus Wein- 

 land (1858) on the grounds that de Blainville (1828) proposed the 

 name Proteocejjhala for a cestode family. Stiles (1901) has rejected 

 Ltihe's conclusions on the grounds that Proteocephalus and Proteo- 

 cephala are not identical and hence not homonyms and that 

 the prior use of a name to distinguish a family does not preclude its 

 later use as a generic name, a point on which we agree with Stiles. 



Liihe (1899) and Braun (1900) regard Tetracotijlus Monticelli, 1892, 

 as a synonym of Icthyotsenia, Liihe giving as his reason that Tetra- 

 cotijlus is preoccupied by virtue of the earlier name Tetracotyle 

 Filippi, 1854. Here again we agree with Stiles (1901) that these two 

 names are not homonyms, but we regard Tetracotylus as a synonym 

 of the earlier Proteocephalus. Monticelli (1892) does not designate 

 a type species. Braun (1900) states that Tetracotylus is based on 

 Tsenia coryphicephala, which is the species Monticelli describes most 

 thoroughly. This action of Braun is tantamount to the designa- 

 tion of a type-species, and T. coryphicephala is here considered as 

 type-species of Tetracotylus by Braun's designation. Braun, how- 

 ever, regards Tetracotylus as synonymous with Icthyotsenia, which 

 makes it a synonym of Proteocephalus for reasons already given in 

 this article. Monticelli gives a list of three new and seventeen old 

 species as belonging in his new genus Tetracotylus, and includes 

 among the old species Tsenia amhigua Dujardin and T.filicoUis Ru- 

 dolphi, the first being the type of Weinland's Proteocephalus and the 

 second an included species. No records are available showing that 

 Tetracotylus has been accepted on the grounds that T. coryphicephala 

 belongs to a genus different from the one to wdiich T. amhigua and 

 T. jilicoUis must be referred, and it is held here to be a synonym of 

 Proteocephalus. 



Tsenia punica Kholodkovski, 1908, should therefore be known as 

 Proteocephalus punicus (Kholodkovski, 1908) Hall, 1910, a combi- 

 nation proposed here for the first time and used in the following key 

 to the tapeworms of the dog. The key is intended to show the rela- 



I 



