440 LARVAL TREMAtODES OF THE NORTHUMBERLAND COAST. 



although they are not far off. The usual moUuscan host for 

 M.flavum is Flanorbis corneus, and that for M. lophocerca is 

 Bythinia tentaculata, both true freshwater Gastropods. 



The specimens of Pahideslriua stagnalis in which these 

 Trematodes were found, were collected from the muddy sand 

 opposite Holy Island, quite close to Beal. Here they live in 

 pools uncovered by the tide for about eight hours a day. 

 They are quite the commonest mollusks in that part, and 

 must serve largely as food for birds, and most probably also 

 for fish. 



Whilst at Stranraer in August and September, 1906, I took 

 the opportunity of observing such Trematodes as were easily 

 obtainable from the common mollusks on the shores of Loch 

 Ryan. Paludestrina stagnalis is one of the common shells 

 of the muddy flats left uncovered by the tide on the east side 

 of the Loch, and in specimens from there I found five of the 

 six Trematodes now described from Fenham Flats. As the 

 proportion of the different species varied considerably in the 

 two localities, it may be useful to compare them. 



It is not unusual for one individual mollusk to harbour 

 several different Trematodes at the same time. It is even 

 stated that one of the common Paludinas has been known to 

 contain as many as nine species at once. In Paludestrina 

 stagnalis not more than two species were found together, 

 viz., Echinostomuni leptosonunn and Cercaria oocysta most 

 frequently in the Fenham Flats specimens, and C. ubiquita 

 and C. lophocerca at Stranraer. 



The Trematodes here described are the following : — 

 From Paludestrina stagnalis : 



Alonostoniiini fiavuni, Melilis. 



Monostoniuin {Cercaria lophocerca, Fil.). 



Cercaria ubiquita. 



C. pirtim. 



C. oocysta. 



Echinostomuni leptosoniuni, Creplin. 

 From Cardium edule : 



Bucephalus hai/ncanus, Lacaze-Duthiers. 



