Trematode Parasites of British Birds. 261 



the intestinal diverticula (but not beyond them). Ova not 

 very numerous, light brown, thick-shelled, measu.ring about 

 •03Gx*019 mm. Yolk-glands, alimentary system, and ex- 

 cretory system as in Tocotrema. 



Looss's subfamily Coenogoniminpe appears too hetero- 

 geneous to constitute a natural subfamily. It seems to have 

 much more the comprehensiveness of a true family, which 

 might be designated Coenogonimidae (or Cotylogonimidse, 

 if, as Braun holds, Liihe's name Cotylogon'wius has jjriority). 

 Moreover, Looss^s definition of his subfamily does not cover 

 the forms which he includes within it. For instance, the 

 following terms do not apply to the genera Tocotrema, 

 Cryptocotyle, and Scap/mnocephahis : — " Body distinctly 

 divided into narrow anterior part and plumper posterior 

 part ; genital aperture in fjont of, or sideways from, the 

 ventral sucker ; long axes of testes transverse to long axis 

 of body ; ovary globular ; Avindings of uterus extend laterally 

 to near the edges of the body; ova "O.^-OS mm. long.^^ 

 That such a family as the Ccenogonimidse exists there can 

 be little doubt, but it is not easy to define its exact limits. 

 Much depends on which features are considered of greatest 

 importance. The genus Ascocotyle appears to indicate a 

 relationship with the Brachycoeliinte, and it is quite possible 

 that the latter, alongwith the genera Spelotrema, Levinseniel/a, 

 and GymnophuUiis, might be included in the same family. 

 The genera Tocotrema, Cryptocotyle, and Scaphanocephalus, 

 Jiigersk., represent the furthest stage which the approximation 

 of the genital aperture with the ventral sucker has reached. 

 They form the nucleus of a subfamily, for which the name 

 Tocotreminse, n. subfam., is appropriate. 



Cryptocotyle concaviun (Crcpl.) ? 



This form occurred very numerously in PhuJacrocorax 

 yraculns; over a hundred examples were taken from one 

 bird. The favourite habitat is the anterior part of the 

 intestine and the duodenum. Dlstomum coucavuia has been 

 recorded by several observers from a large number of hosts. 

 Miihling^s description of the species is the most exhaustive, 

 and he was the hrst to discover the true nature of the genital 

 sucker, but my specimens do not entirely coincide with his 

 description. 



A prepharynx is not entirely absent, but is short, being 

 only i of tlie length of the pharynx. The oesophagus is also 

 slightly shorter than the pharynx, and thus much shorter 



