246 ^{r. W. iS^icoll on the 



The species obtained appeared on a first examination to 

 be all assignable to well-known genera, e. g. PsUostomum, 

 Echinostomum, Gymnoph alius, Tocotrema, and in particular 

 Spe/otrema. The frequent occurrence of members of the 

 last-named genus was not surprising, as I had previously 

 found a Spelotremn species in great abundance in Larus 

 argent atns. A great variety of sizes occurred, but in this 

 respect there were no obvious lines of demarcation to 

 indicate whether one or more species were under considera- 

 tion. Closer examination proved that not only were there 

 several different species, but that two distinct genera were 

 jn-esent. They occurred, as a rule, side by side in the same 

 liosts, occupying the same situations in the intestine and 

 being equally numerous. I have been able to differentiate 

 three distinct species of Spelotrema, as well as three species 

 of the other genus, which is new and for which I propose 

 the name Maritrema. In addition a new species of Gymno- 

 phaUus and one of Tocotrema have to be recorded. 



Altogether 16 species of birds were examined. Of these, 

 three, Urinator lumme, Alle alle, and Uria troile, yielded no 

 Trematode parasites. Of the other species 91 per cent, of 

 the examples were more or less abundantly infected. Of 

 the total number of all species 68 per cent, were infected. 

 These figures are very high com])ared with those of Miihling^, 

 Ilausmann tj and Wolffhiigel $, but this is perhaps to be 

 accounted for by tbe fact that I do not include any purely 

 terrestrial birds (in the sense that they do not frequent 

 the sea), which are apparently much less subject to infection 

 than the shore-birds. Other possible explanations are that 

 this locality is more favourable for infection, or that my 

 examination has been more exhaustive than that of the 

 above-mentioned observers. 



The absence of Trematode parasites in Alle alle and Uria 

 troile recalls a similar condition § in Blennius pliolis amongst 

 fishes. Both these birds are, so far as 1 know, purely 

 aquatic and feed principally on crustaceans and fish. The 

 shore-birds, on the other hand, live to a large extent on 

 mollusks, as well as fish, the diet being thus in great part 

 different. In the same way the diet of Blennius pholis, 

 which subsists on small mollusks 1|, differs from that of other 



* Arcbiv f. Naturg. Ixiv. p. 58. 

 t Centralbl. f. 13akter. xxvi. p. 452. 



+ Beilra"' znr Kenutuis der Vogellielmintlien (Inaug.-Diss.), 1900. 

 § Ann. & Mag. Nat. Hist. (0) xix. p. 68. 



II Blennius pliolis is also fond of Balanus, but tbe sessile condition 

 of tbe latter renders it dillevent from otber C'nistacea. 



