1911] Watson: The Genus Gyrocotyle. 357 



"Corpus sub-ellipticum depressum; os subterminale corpore con- 

 tinuum; os subterminale anticum exiguum; acetabulum unum in extremi- 

 tate caudali terminale, sessile, orbiculare, disce in gyros plicata; penis 

 ventralis superus lateralis; apertura feminea infra penem centralis; 

 porus excretorius dorsalis supra acetabulum." [Quoted from Braun 

 (1889)]. 



The genus as thus denned contained only a single species, 

 Gyrocotyle rugosa. Diesing referred the genus to the trematodes, 

 placing it near the genus Amphistomum because of the posterior 

 position of its acetabulum. In 1855, in his description of the 

 collection of endoparasitic worms made by Natterer in Brazil, 

 Diesing published a second description of the genus identical 

 with the first, with five figures and a discussion of the habitat 

 and systematic affinities of the genus. He regards it as improb- 

 able that both Mactra edulis and Antilope pygarga are true hosts 

 of Gyrocotyle, and believes that the report of its occurrence in 

 Mactra is an error. In case Mactra should prove to be the true 

 host, he concludes that Gyrocotyle as an ectoparasite would have 

 to be referred to the Bdellidea. As an endoparasite of Antilope, 

 he places it under the trematodes. Diesing made no attempt at 

 a study of the internal structure of the parasite and apparently 

 only a cursory examination of its external appearance. From 

 his figures it seems probable that his specimens were in a state 

 of decomposition when preserved. 



In 1852 Wagener described and figured a parasite found by 

 himself and Grube in the spiral valve of Chimaera monstrosa, 

 at Nice. For this he established the genus Amphiptyches, con- 

 taining a single species, urna, and referred this genus to the 

 cestodes because of its morphological resemblance to that group. 

 Wagener made a careful study of the internal structure of the 

 worm, both in the living animal and preserved specimens made 

 partially transparent by clearing. Except for confusion, as to 

 the ducts of the genital organs and in a few minor details, his 

 figures are correct. Diesing 's (1855) description and figures 

 convinced Wagener that Amphiptyches was identical with Gyro- 

 cotyle. In a letter to Diesing (1857) he calls the latter 's atten- 

 tion to Amphiptyches urna, and in his ' ' Enthelminthica No. V. ' ' 

 (Wagener, 1858), he discards Amphiptyches as a generic name 

 and retains it as a specific name for the form discovered by him : 



