468 WILLIAM NICOLL. 



These 102 species represent practically all the marine fishes commonly 

 occurring in British seas. Little more than 20 others have ever been re- 

 corded from the British coasts, and the majority of those only as isolated 

 individuals. 



Apart from these investigations only four species have been recorded 

 in British waters as hosts of trematode parasites, namely, Brama rail, 

 Phycis hlennoides, Raia radiata, and Trygon pastinacea. 



In addition to the four above-mentioned localities, the trematode 

 parasites of marine fishes have been pretty exhaustively dealt with on 

 the Northumberland coast by Miss Lebour and on the Lancashire coast 

 by Johnstone and A. Scott. From these investigations a fairly compre- 

 hensive idea may be obtained of the trematode fauna inhabiting our 

 marine fishes. It seems desirable, however, that further investigations 

 should be made in such areas as the Bristol Channel, the north-west 

 coast of Scotland, or the Hebrides, and the southern part of the North 

 Sea (e.g. off Lowestoft). In particular it would be interesting to obtain 

 information as to the trematode fauna of fishes from the coast of Ireland, 

 a region still practically untouched. 



Of the 475 fishes examined at Plymouth, 380 (80%) were infected with 

 parasitic worms : 56% were infected with Trematodes, 44% with Ces- 

 todes, 48% with Nematodes, and 2% with Echinorhynchs. 



It is interesting to compare these figures with those obtained in other 

 areas. The comparison is shown in the following table : — 



Total . . 60% 47% 56% 5% 81% 



This table shows that although the percentage of infected fishes in 

 the Plymouth area is only slightly less than that in the other areas, yet 

 the variety of parasites in each fish is considerably less. It will be seen 

 that the Plymouth figures are less in every case than those of other 

 areas with the single exception of the incidence of Trematodes in the 

 Aberdeen fishes. 



In the present report only the trematode parasites are dealt with. 

 Over 50 different species were collected, and these represent about 

 three-fifths of the total number of Trematodes known to occur in British 



