272 s. GOTO. 



They are mostly confined to the marginal part of the body, but 

 are also present, although sparsel}'-, on the more internal parts. 

 They are somewhat similar to the chitinous corpuscles of Tr. 

 coccineum and Tr. 7noke. Each corpuscle consists, namely, of a 

 basal rounded portion imbedded in the investing membrane of the 

 body, and a projecting portion which is either bi-, tri-, or quadri- 

 cuspid (fig. 10). They are of various size, the smallest ones 

 being about 10 fi across at the base and the largest ones being 

 three times as large. They do not form transverse rows, as in 

 Tr. coccineum, nor do they form such a regular longitudinal row 

 on either side of the body, as in Tr. sinuaiujn and Tr. biparasi- 

 ileum, but are scattered singly in the marginal portion of the 

 body, on the dorsal side. The most external ones, however, 

 tend to form a longitudinal row. It is needless to remark that 

 these chitinous corpuscles are entirely absent in the specimens of 

 Tr. ovale. 



The second point of difference between the forms under 

 consideration lies in the difference in size of the hooks in the 

 posterior sucker. In the specimen of Tr. levé they measure 0.63 

 mm. in length, while in Tr. histiophori they are 0.85 mm. long. 

 In Tr. ovale they are 0.91 mm. This diff'erence between Tr. 

 histiophori and Tr. ovale may perhaps be attributed to errors 

 of observation, but the difference between Tr. ovale and Tr. levé 

 can not be so accounted for. With all this difference in size, 

 the hooks are remarkably similar in form in all the three 

 forms. 



With the facts above detailed in mind I propose to amal- 

 gamate the three species, Tr. levé Verrill, Tr. histiophori Bell, 

 and Tr. ovale Goto into one, which, agreeably to the law of 

 priority, must be called Tristomum levé Verrill, and to distiuguish 



