1911] Watson: The Genus Gyrocotyle. 365 



The examination of C. colliei for parasites has yielded the 

 following results : 



(1) The fish is almost invariably infested with a parasite 

 belonging to the genus Gyrocotyle. The parasite was- found in 

 34 of the 38 specimens examined. 



(2) The parasite rarely occurs singly, but usually two indi- 

 viduals in one host. More than three in one fish I have never 

 found. In four cases a single individual was found. 



(3) No other adult cestodes have been found in the alimen- 

 tary tract of the fish. Encysted cysticerci are common in the 

 walls of the tract, in the mesenteries, liver, etc., especially during 

 the summer months. Parasitic crustaceans were frequently 

 found on the gills, and an aspidocotylean, probably belonging to 

 the genus Macraspis, was found embedded in the muscles of the 

 rectum. A distome, bearing a strong superficial resemblance to 

 a small Gyrocotyle without frills, was found once in the posterior 

 region of the rectum, and once in the body-cavity. 



(4) Two distinct species of Gyrocotyle are found in C. col- 

 liei; one, the less common of the two, is closely related to and 

 perhaps identical with, Gyrocotyle urna; the other differs in 

 several characteristics from any species heretofore described. 

 The incompleteness of the figures and descriptions of G. urna 

 make it impossible to determine accurately the identity of the 

 form first mentioned with G. urna. It will be referred to as G. 

 urna (var. ?) . The second form, which, in view of its well-defined 

 peculiarities and of the absence of any intermediate forms link- 

 ing it to any described form, I regard as a new species, will be 

 refered to as G. fimbriata. 



Gyrocotyle fimbriata, sp. nov. 



Diagnosis. Color, creamy white ; length 30-55 mm, width 

 7-12 mm.; rosette posterior, folds complex; lateral frills 3-5 mm. 

 deep, much folded, passing into smooth lateral fin near anterior 

 extremity; spines numerous, distributed in definite pattern, 

 points directed anteriorly; eggs about 0.09 mm. in average long 

 diameter, no hooked embryos; penis opens mediad of vagina, at 

 about the same antero-posterior level. Occurs in spiral valve of 

 Chimaera colliei; can leave host and live for some days free. 



