TREMATODES OF THE NORTHUMBERLAND COAST 3 1 



suckers are much the same, but the intestine of the present 

 worm is larger and extends further down the body. It differs 

 from the ' Pearl Trematode ' described by Jameson and 

 NicoU* in its smaller size, conspicuous head glands, larger 

 intestine, greater size of the oral sucker in relation to the 

 ventral, and in the shape of the excretory vesicle. The 

 cercaria found by Levinsenf in Saxicava rugosa, as well as 

 Jameson's 'Pearl Trematode', is referred by Odhnerf to 

 Gymnophallus bursicola, Odh., which also occurs in the Eider 

 Duck, and agrees with these cercariae far more closely than 

 does G. somatericB, to which species Jameson originally referred 

 his worm. Nicoll§ however considers that his new species 

 G. dapsilis from Oideitiia fusca and O. Jtigra (Velvet Scoter 

 and Common Scoter) has equally strong claims to be re- 

 garded as the adult of the * Pearl Trematode.' Cercaria 

 glandosa occurs in about ten per cent, of the Paludestrina 

 stagnalis from Fenham Flats near Holy Island : it is usually 

 found singly, but as many as six specimens have been counted 

 in one animal. 



Cercaria macom^, nov. (Plate I., fig. 2.) This cercaria 

 occurred in several specimens of Macoma balthica from Fenham 

 Flats, between the mantle and shell. Two or three specimens 

 were sometimes found in one mollusk. It is oval and measures 

 0-70 mm. in length when at rest. The body is covered with 

 spines and is very transparent. The oral sucker measures 

 o-22-o"26 mm. in diameter and the ventral 0*06-0.07 "im. 

 The latter is situated well behind the centre of the body and 

 its inner margin is crenulated. The oral sucker leads to a 

 small pharynx, and this to a short oesophagus branching into 

 two broad intestinal lobes without much food inside, and in 



* NicoU, TV., "Notes ou Trematode Parasites of the Cockle (Cardium edule) and 

 Mussel (Mytilus edulis)," Ann. and Mag-. Nat. Hist., Ser. 7, Vol. XVII., 1906, p. 148. 



t Levinsen, O.M.R,, "Bidrag til Kundskab om Grononlands Trematodfauna," 

 Overs. K. D. v. Selsk. Forh., 1881, p. 52. 



\ Odhner, T,, " Die Trematoden des Arktisohen Gebietes," Fauna Arctica, 1905, 

 p. 313. 



§ XkoV, W,, " Observations on tlie Trematode Parasites of British Birds," Ann. 

 and Mag. Nat. Hist., 8cr. 7, Vol. XX., 1907, p. 265. 



