84 
Buccinum undatum is one of the commonest articles of food of 
the catfish. Remains of it are constantly to be found in the 
stomach. The specimens examined came from rocky ground where 
the catfish is to be found living almost entirely on mollusca and 
where Buccinum undatum is one of the commonest forms to be met 
with. It is, therefore, extremely probable that this cercaria and 
the adult worm from the catfish are identical. 
I have named this Trematode Acanthopsolus lag eni for mis from 
its flask-like form. The most important differences from Acanthop- 
solus oculatus (Levins), the only liitlierto-known member of the 
genus, consist in the position of the testes which are symmetrically 
placed one on each side of the body instead of obliquely as in 
A. oculatus, and in the presence of a receptaculum seminis which is 
said to be absent in A. oculatus. The eggs are enormous for the 
size of the worm, far larger in proportion than those of A. oculatus. 
These differences do not seem to j istify the founding of a new genus 
for this worm, especially as the receptaculm seminis often appears 
to be absent when not full of sperms. I would, therefore, alter 
slightly the present diagnosis of the genus so as to make it include 
A . lageniformis : — Small distomes with delicate body rounded before 
and behind, which is divided into a very moveable flattened fore 
part and a plump hind part more circular in section. Skin very 
thin, armed with scales. Intestine with long prepharynx, pharynx 
of medium size, extremely short ’oesophagus. Fork of the intestine 
a little in front of the ventral sucker. Intestinal coeca similar, 
reaching to the hind end of the body. Excretory vesicle a simple 
sac. Genital pore median immraediately in front of the ventral 
sucker. Male and female copulatory organs strongly developed, 
armed with thorn-like spines. Cirrus sac club-shaped, rather long, 
containing a bilobed seminal vesicle, an apparently weakly developed 
pars prostatica and a long cirrus covered with spines. Testes in the 
hind body, lying obliquely belli id one another or symmetrically 
placed on each side of the body. Ovary on the right, in front of 
the testes or nearly at the side of the foremost testis. Laurer’s 
canal present, receptaculum seminis present or absent. Vitellaria 
with big follicles, especially under the dorsal surface and at the 
sides of the body. Shell gland dorsal, at the side of the ovary. 
Uterus loops between the ventral sucker and genital glands. Eggs 
few in number, very big (about 0-125 mm. long) tliin-walled. 
Inhabits intestines of marine fish. 
