200 Mr. W. Nicull on the 



towards tlie middle line. Just in front of the pharynx they 

 unite in the middle line, forming a wide commissure. From 

 this a short wide branch runs forward on each side. Ovary 

 situated immediately behind the ventral sucker, median or 

 somewhat to the right ; it has a characteristic trilobate out- 

 line, the base facing outwards and the apex median. Uterus 

 very voluminous, occupying the greater part of the body 

 behind ovary, but not extending in front of the latter. Ova 

 numerous, oval, colourless on left side of bodv, yellow on 

 right. Size •016--022 x 008-012 mm. Yolk-glands of 

 limited extent, confined to a fringe along the edge of the 

 posterior part of the body. At the level of the testes this 

 fringe bends inwards, passing along the anterior border of 

 testes to unite in the middle line, so that almost a complete 

 circle is formed. Receptaculum seminis absent (?). Laurer's 

 canal (?). Testes symmetrical about the middle line, a little 

 behind the ovary ; outline oval, long axis usually transverse, 

 sometimes decidedly oblique. Vesiculaseminalis large, oval, 

 on the right side of and close to the ventral sucker, behind 

 which it extends some distance. It is enclosed in a well- 

 marked cirrus-pouch. This has a somewhat pear-shaped 

 outline, narrowing in front of the vesicula seminalis. The 

 narrow part contains a short pai's [)rostatica and passes round 

 in front of the A'entral sucker. The genital aperture is on 

 the left of the latter, a little behind the level of its anterior 

 border. The vagina passes up on the left side of the 

 sucker. 



Habitat, the intestine of birds. Type, Mariirema gratio- 

 sum, sp. n., from Pelidna alpina. Other species, M. lepidwn, 

 sp. n., and M. Jmmile, sp. n. 



Mariirema gratiosum, sp. n. 



This occurred frequently in large numbers in Pelidna 

 alpina and yEgialitis hiaticula. A few immature specimens 

 from Larus ridibundvs and Hcematopus osiralegus are pro- 

 bably best referred to this species, although they do not 

 wholly agree with the mature examples. The habitat is 

 most usually the anterior part of the intestine. 



The body is flattened and somewhat elongated, with a 

 tendency to assume a tongue-like outline. There is usually 

 a slight constriction near the level of the ventral sucker. 

 The length varies from '45 mm. to i'lO mm., the maximum 

 breadth from '24 mm. to "44 mm., or l-^ of the length. As 

 in Spelolrem.a species, considerable difficulty was experienced 

 in determining the relative sizes of the suckers. Of the 



