NO. 1780. A NEW CE8T0DE PARASITE— HALL. 147 



It is obvious that if these two genera are strictly synonymous, 

 Proteocephalus must be retained by virtue of many years priority. 

 Whether they are synonymous depends on the application of Wein- 

 land's Proteocephalus. Unfortunately, Weinland selected as a type 

 species Tsenia amhigua Dujardin. This has been stated by Liihe 

 (1899) to be at present a species inquierenda. In the same article, 

 Liihe raises the point that he himself has created the new genus 

 Nernatotsenia and taken as its type Tsenia dispar, the last of the three 

 species mentioned by Weinland. Proteocephalus is left then with a 

 type species, Tsenia amhigua, now regarded by Liihe as a species 

 inquierenda, and the included species Tsenia jilicoUis, which latter 

 species Liihe (1899) regards as identical with Icthyotsenia ocellata 

 (Rudolphi) Lonnberg. Unless Icthyotxnia applies to forms generically 

 different from those of Proteocephalus it must fall into synonymy by 

 virtue of the law of priority. A consideration of Dujardin's (1845) 

 descriptions of Tsenia amhigua and Tsenia filicollis {Icthyotxnia 

 ocellata) does not warrant us in considering the two species generically 

 different, and unless this can be shown, the generic characters of 

 Proteocephalus may be taken from the better known Tsenia filicoUis 

 in the absence of adequate data regarding T. amhigua, since Wein- 

 land mentions T. filicollis as belonging in the genus Proteocephalus. 

 In other words, unless sufficient data exist to warrant a belief that 

 the type species and the included species of a given genus are generic- 

 ally different, they should be considered as generically identical and 

 the characters of the genus regarded as fixed by the included species 

 in the absence of the type material. Liihe (1899) apparently believes 

 that such data exist in the case of Tsenia dispar and proposes for it 

 the generic name Nematotsenia. The only distinguishing character 

 suggested in proposing the name, the circular cross section of the 

 proglottids, is one already noted by Dujardin (1845). No such 

 adequate difference has been shown to exist in the case of Tsenia 

 amhigua and T. -filicollis and in our opinion such differences are not 

 indicated in Dujardin's descriptions. 



Lonnberg (1894), in proposing the name Icthyotsenia for certain 

 fish tapeworms, was apparently unaware of the existence of the 

 generic name Proteocephalus and gave it no consideration. In mak- 

 ing T. filicollis the first of his so-called type species, he made Icthyo- 

 tsenia a synonym of Proteocephalus, unless it can be shown that 

 good reason exists for considering T. amhigua, the type of Proteo- 

 cephalus, generically distinct from the included species T. filicollis, 

 which is type of Icthyotxnia. Railliet (1899) states that T. amhigua 

 falls clearly in the genus Icthyotxnia,, and that Proteocephalus should 

 be retained on the grounds of priority. The only evident reason 

 why Braun (1900) and others should make Proteocephalus a syno- 



