Trematode Pcvasiites of British Binh. 2(57 



specimens measured about 60 per cent, showed the oral 

 sucker greater than the ventral, but taking the average of 

 the tigures obtained it was found that both approximated 

 •050 mm. The limits in each case are •043-'062 mm. The 

 suckers are therefore very nearly equal, the oral sucker 

 being usually a little the larger. In the immature specimens 

 from Hcematopus and Larus ridibundus the oral sucker is 

 invariably distinctly greater. The oral sucker is subterminal 

 and the ventral sucker is ahnost midway between the anterior 

 and posterior ends of the body. The prepharynx is usually 

 of considerable length, '062 mm. on an average^ being nearly 

 twice as long as the pharynx, which measures "OSS X "OIG inm. 

 In the Hcematopus and Larus specimens the prepliaryux Avas 

 usually much shorter. The oesophagus measures 'OG-IG mm., 

 being \—^ of the body-length. The diverticula are more 

 than twice as long, "IG-'Sr mm., and this forms an important 

 point of difference between this species and the other two 

 .species of the genus. They always extend as far back as the 

 anterior border of the testes. 



The ovary is situated immediately behind the ventral 

 sucker, median or a little to the right. The characteristic 

 trilobate outline is well marked. The uterus is so voluminous 

 that its convolutions cannot be followed. It first fills the 

 h^ft side, where the ova are colourless, then passes to the 

 rjght, where they are yellow in colour ; the condition is 

 ims the reverse of that in Spelotrema. The numerous ova 

 ineasure -020-022 x •010-'012 mm. The yolk-glands have 

 the situation and extent already noted in the definition of 

 tiie genus, and this is constant for all three species. The 

 testes are not overlapped by the uterus to any great extent, 

 so that they are probably almost as thick as the body itself. 

 Their outline is elongated oval, and their long axes are 

 directed more or less obliquely upwards towards the middle 

 line. In the specimens from Larus ridibundus the long axes 

 are directly transverse, while in those from Htematupus the 

 testes are almost globular. The shape and position of the 

 cirrus-pouch have been noted in the definition of the genus. 

 The vesicula senunalis within the pouch had a perfectly oval 

 ou;bne and is proportionately suuiUer in this species than in 

 the ('ther two. It does not extend much further back than 

 the middle of the ovary. The terminal portion of the vagina 

 has a sinuate course. 



Maritrema lepidum, sp. n. 



This occurred only in the intestine of Larus argent atuit. 

 It is jl,out the same size as the previous species, but differs 



15* 



