Trematude Parasites of British Birds. 263 



of the body, and the uterus traversed the body only twice. 

 The possibility of amphitypy and slight error on Miihliug's 

 part causes me to hesitate in separating my specimens 

 specifically from Distomum concavum. I therefore inckide 

 them under that species for the present^ in the hope that 

 further investigation will prove them identical or distinct. 



My specimens varied in length from "68 mm. to 1"06 mm., 

 and in breadth •40-*66 mm., the average size being 

 •81 X "54 mm. The maximum breadth is therefore f of the 

 length. The oral sucker has an average diameter of •060 mm., 

 and the genital sucker measures '15 x "11 mm. The size of 

 the ovary is about "IS x "07 mm. 



Genus Gymnophallus, Odhner. 

 GymnophalJus dapsilis, sp. n. 



Occurred frequently in the Bursa Fabricii of Oidemia fusca 

 and Oidemia tii/jra. It resembles in its habitat and in other 

 respects Gymn. bursicohi, Odhn., from Somateria moUissima. 



It differs from all other species of the genus iu having the 

 yolk-glands in front of the ventral sucker, and this is the 

 principal difference between it and Gymn.bursicola. Mature 

 specimens varied in length from ^84 mm. to 1"13 mm,, the 

 average being very approximately 1 mm., and, in fact, most 

 of the examples varied but little from that size. One speci- 

 men '7o mm. long contained ova, but it was an exception. 

 Immature forms were found as small as '68 mm. The 

 maximum breadth at about the middle of the body was 

 •45-80 mm., average '63 mm., or nearly | of the length. 

 The general outline is a regular oval with rounded ends. 

 The cuticle is entirely covered with sharp scales, 'OOG mm. 

 long ; it gives the body a firm consistency and when ruptured 

 by pressure the fracture is sharp. 



The oral sucker is circular, with a diameter of •1G-*21 mm., 

 i. e., about 1 of the body-length. The ventral sucker is 

 smaller, -14-' 17 mm., and lies almost exactly \ of the body- 

 length from the posterior end. In immature specimens the 

 suckers tend to be more nearly equal. The pharynx is con- 

 tinuous with the mouth and is almost circular in outline, 

 with a diameter of •068-087 mm. The oesophagus is about 

 the same length as the pharynx. The diverticula are short 

 and wide and extend very slightly beyond the middle of the 

 body. The excretory vesicle resembles that of Gymn. bursi- 

 cola, but the bifurcation is nearer the ventral sucker. The 

 limbs end near tlie edge of the body at the level of the 

 pharynx. 



