2 OSBORN. [Vol. XVIII. 



he found in the Unionidse of the Schuylkill River. His account, 

 which is sufhciently adequate for taxonomic purposes, is very 

 brief and does not extend to details of morphological value. 

 Leidy in his notice in 1858 expressed the opinion that Cotylaspis 

 may be a stage in the life cycle of Aspidogaster, but this proved to 

 be incorrect. In 1884 Poirier, in a paper describing a number of 

 different trematodes, devotes two pages to a summary of the 

 anatomy of a form which was found in a turtle {Triarthra] in 

 the Senegal River in Africa, and which he referred to the genus 

 Aspidogaster, making it a new species, A. lenoiri. This account 

 is confined to the coarser, anatomical facts. In 1893 Braun re- 

 ported the facts of Poirier's article in Bronn's Klasscn imd Ord- 

 nimgen. In 1892 IMonticelli revised the Aspidobothridse in his 

 contribution to Leukart's Festschrift volume. He saw the neces- 

 sity of separating Poirier's fluke from the genus Aspidogaster, 

 and instituted a new genus, Platyaspis, for it. In 1898 the pres- 

 ent writer reported the anatomy of a fluke found by him in the 

 Anodontas of Lake Chautauqua in 1895, which presented such a 

 close resemblance to the form found by Poirier in Africa as to 

 convince him of their generic similarity, and relying on the work 

 of Monticelli an account of it was published under that name. 

 This was followed by an article by Professor C. A. Kofoid in 

 1899 in which he pointed out the fact that the Platyaspis of my 

 former paper is undoubtedly identical with Leidy's Cotylaspis, 

 and the further fact that Platyaspis in jMonticelh's sense differs 

 from Cotylaspis in one particular, the marginal organs of the ven- 

 tral sucker, to which reference will be made later in the course of 

 this paper. 



The object of this paper is to place on record the facts as at 

 present known in regard to this member of the family Aspido- 

 bothridje, a family of great interest to students of the Trematodes, 

 yet one in regard to some of the members of which almost noth- 

 ing has until recently been known. Our knowledge of the family 

 hitherto rests on the studies that have been reported by Voeltzkow 

 and Stafford of Aspidogaster, by Monticelli and quite recently 

 Nickerson of Cotylogaster, and by Nickerson of Stichocotyle. In 

 addition to these genera the anatomy of which is adequately 

 known, we have briefer records of Macraspis, Cotylaspis, and 



