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Part III. — Twenty-eighth Annual Report 



VII.— XOTES ON SOME TREMATODE PARASITES OF FISHES. 

 By Thomas Scott, LL.D., F.L.S. 

 (Plates YTI. ; VIII.) 



One or two papers on parasitic Trematodes of fishes have already appeared 

 in Part III. of the Annual Reports of the Fishery Board for Scotland, 

 published in previous years. In the present paper four species, in addition 

 to those previously published, are recorded, one of which appears to be 

 undescribed.* 



TREMATODA. 



Fani. Tristomatid/E. 



Genus Callicotyle, Diesing (1850). 



Character. — Body thin, tolerably expanded ; posterior sucker discoidal, 

 nearly sessile, and provided with seven rays and two spines ; the mouth 

 without suckers. 



Callicotyle affinis, new species. PI. VII., fig. 1. 



The Trematode recorded here has a close resemblance to Callicotyle 

 kroyeri, Diesing, found on various kinds of skates (Raia clavata. radiata. 

 and batis), but one or two obvious differences prevent its inclusion in the 

 same species, and as I do not know of any other to which it can be ascribed, 

 the name Callicotyle affinis may be given to it. 



It differs from CaiUcotyle kroyeri in size, being nearly one and a half 

 times longer ; in shape it is broadly ovate, and the greatest width, which is 

 near the middle, is equal to rather less than half the length ; the width of 

 the posterior half does not vary much, but the anterior half becomes 

 gradually narrower towards the bluntly rounded apex. 



The posterior sucker is transversely broadly ovate, the width exceeding the 

 length by about one-fifth ; the anterior margin is broadly and evenly 

 rounded, but the margin opposite is flattened and somewhat sinuate. 

 Interiorly this sucker has, like that of CaiUcotyle kroyeri, seven submarginal 

 compartments and a central one ; the lowermost of the seven compartments 

 is in the middle line, and has on each side a slightly curved tooth; the 

 centre compartment is not round as it is in Callicotyle kroyeri, but trans- 

 versely narrow. There are apparently no suckers at the anterior end, and in 

 this respect it also agrees with Callicotyle kroyeri. 



The length of the specimen represented by the drawing (fig. 1) is 9 mm. 



Habitat. — Parasitic on the gills of Chimera monstrosa, Linne, captured 

 in the North Sea, January 1910. Apparently rare. 



Fam. POLYSTOMATID^E. 



Posterior suckers more or less numerous. 



Genus Octobothrium, Leuckart (1828). 



Trematodes provided with eight posterior suckers and usually with a 

 small one on each side of the mouth at the anterior end. 



* I am indebted to my colleague, Dr. Williamson, for the privilege of examining 

 the fishes on which the organisms recorded here were obtained, and to my son, 

 Andrew Scott, A.L.S., for the drawings and photographs. 



