yo8 MacCALLUM. [Vol. XV. 



and female openings situated posterior to the acetabulum, either 

 about halfway between the acetabtilum and posterior extremity 

 (as in the type Clinostomum gracile), or immediately posterior to 

 the acetabjihim, as in D. Westermanni, Kerbert. Oral sticker 

 without tentacles or spines : Caudal extremity without retractile 

 appendage. Intestine simple, bifurcate. 



Thus there are contained in this description two groups of 

 flukes, which will probably later be parted into separate genera. 



I wish to express my thanks for literature, etc., to Prof. R. 

 Ramsay Wright, of Toronto University, whose readiness to aid 

 me in my work has been unfailing ; also, to Drs. Stiles and 

 Hassall, of Washington, whose library and specimens I have 

 made use of, and who have been very kind in advising me with 

 regard to the questions of nomenclature. 



Baltimore, October lo, 1897. 



