360 University of California Publications in Zoology. [ VoL - 6 



organization to that of the cestodes is then pointed out in the 

 musculature, the lack of a digestive tract, the arrangement of 

 the excretory system, the general form of the nervous system, 

 the arrangement of the genital organs, and the presence of a 

 six-hooked embryo, in Gyrocotyle rugosa. 



In the same year (1889c), in examining the Entozoa of the 

 British Museum, Monticelli found an undoubted example of 

 G. rugosa, taken from Callorhynchus antarcticus at Dunedin, New 

 Zealand. As he points out (1890), G. rugosa had up to this time 

 been reported only from Mactra edulis, G. urna only from 

 Chimaera monstrosa. He summarizes his conclusion as follows : 



"1. Che il genere Gyrocotyle e parassita proprio della famiglia delle 

 Chimaeridae. 



"2. Che i due generi finora conosciuti della famiglia (Chimaera e 

 Callorhynchus) albergano ciascuno una specie del genere Gyrocotyle. 



"3. Che il genere Gyrocotyle perviene nelle Chimaeridae per mezzo 

 di molluschi bivalvi. " 



Monticelli discusses the question whether Mactra edulis is to 

 be regarded as the true intermediate host of G. rugosa, and con- 

 cludes that, since the example found in the mollusk contained 

 hooked embryos, a third host must be found to convey G. rugosa 

 to Mactra. He suggests that possibly some of the mollusks on 

 which Chimaera monstrosa feeds (probably some member of the 

 Cyprinidae), may be the intermediate hosts of G. urna. 



This work of Monti celli's definitely settles the question as to 

 the generic identity of Gyrocotyle and Amphiptyches, and estab- 

 lishes two species of the genus Gyrocotyle, separated by three 

 distinct characters. Further, it indicates that G. rugosa is a true 

 parasite of Callorhynchus, though this point could hardly be 

 considered as established by a single occurrence of the parasite 

 in the fish. 



Further evidence on this question was supplied by Spencer's 

 (1889) report on the morphology of three specimens of Gyro- 

 cotyle found by him in the mouth of a specimen of Callorhyn- 

 chus antarcticus. These Spencer referred to Wagener's Amphi- 

 ptyches urna, but from the form of the lateral frills and the 

 presence of hooked embryos, it seems quite clear that his species 

 was not G. urna, but G. rugosa. (See my pi. 38, fig. 36). This 



