ECTOPARASITIC TREMATODES. 271 



Tristomum levé Verrill. 



Syn. — Tristomum, hîstiophorî Bell. f'9l.] 

 TristomAim ovale Goto. ['94.] 



In the original description of Tristomum ovale ['94, pp. 241- 

 244] I expressed the suspicion that it might prove identical 

 with tlie TV, histiophori of Bell ['91], and in a sectional meeting 

 of the Third International Congress of Zoologists held in Leyden, 

 I stated that Tr. ovale Goto must be regarded as a synonym of 

 Tr. /ere Verrill [75, p. 80; '85, pi. 43]. This latter conclusion 

 was based on an examination of a type specimen of Tr. levé, 

 which was kindly given me by Prof. Verrill. Subsequently, on 

 my visit to the British Museum, Prof. Bell was so kind as to 

 give me some specimens of Tr. histiophori ; and a comparison of 

 these specimens with each otlier and with those of Tr. ovale has 

 brought to light some additional facts which further elucidate 

 the affinity of these forms. 



The specimen from Prof. Verrill is rather old, but the im- 

 portant points can all be made out. The external features of 

 the body as well as the arrangement of the internal organs are 

 exactly similar to what I have observed in Tr. ovale, except in 

 two points ; viz. the length of the hooks in the posterior sucker 

 and the presence of numerous chitinous corpuscles on the dorsal 

 surface of the body. These corpuscles were noticed by me from 

 the first, but as there was a crusty precipitate on the S23ecimen 

 before mounting, I was not quite sure whether these corpuscles 

 were really chitinous structures belonging to the worm or whether 

 they were not extraneous encrustment. The presence of similar 

 corpuscles in the specimens of Tr. histiophori has, however, 

 convinced me that they were integral parts of the worm. 



