M. V. Lebour 
445 
like E. leptos^muvi. Almost every mussel at Budle contains these 
cysts and about 10 per cent, of the cockles. It is also common at 
Fenham Flats and Loch Ryan encysted in the mussels and cockles. 
The final host according to Nicoll (ill. 1906, p. 515) is the oyster 
catcher Haeniatopus ostralegus, also the herring-gull Larus argentatus 
and the black-headed gull L.Tidihundus, ’m which hivds axi Echinostontum 
occurs, which was traced by Nicoll from very young forms almost 
exactly corresponding to the above-mentioned cercaria to the adult.s, 
which he has described as E. secundum. I think from the evidence 
of the cercariae and rediae there is no doubt that these are distinct 
species. The third form which I believe to be also a distinct species 
is described below. 
Echinostomum sp. 
Cercaria littoidnae ohtusatae sp. inq. 
(PI. XXVIII, figs. 15-17.) 
Occurs in the digestive gland of Littorina ohtusata from Millport 
in about five per cent. It looks a pale yellowish-brown when infected 
but the redia is quite colourless and peculiar in having an extremely 
small pharynx and intestine even in the young forms. The smallest 
redia seen was 0'5 mm. long, of a squarish form with a conspicuous 
collar and more or less pronounced ambulatory processes. Pharynx 
very small with intestine not reaching half-way down the body. The 
older rediae measured 2—3 mm. in length, the pharynx so inconspicuous 
that it was difficult to see it at all and the intestine is actually smaller 
than in the youngest redia seen. The large rediae were full of cercariae 
in various stages. 
The cercaria is extremely like E. secundum, the smaller head spines 
however are not so short as those in E. secundum. Length of body 
0'78 mm., tail 0'4 mm. long. Body covered with spines for the first 
two-thirds of its length. 29 head spines. Oral sucker 0'06 mm. across, 
ventral sucker 0 08 mm. across. Excretory system with much branched 
lateral canals, the granules contained in them soon disappearing so that 
the clear canals are specially easy to see, and the part continued into 
the tail can clearly be made out bifurcating a little more than half-way 
down. In E. leptosomum and E. secundum it also is continued into 
the tail but cannot be so clearly seen. 
The further life-history of this species is not known. 
