Trematode Parasites of British Birds. 261 



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

 very numerou.s, light l)rown, thick-shelled, measuring about 

 •OcJGx-019 mm. Yolk-glands, alimentary system, and ex- 

 cretory system as iu Tucutremu. 



Jjooss's subfamily Coenogoniminfe appears too lietero- 

 geneous to coustitute a natural subfamily. It seems to have 

 much more the comprehensiveness of a true family, which 

 might be designated Coenogonimidie (or Cotylogonimidse, 

 if, as Braun holds, Liihe's name Cotyloyonimus has jiriority). 

 Moreover, Looss's detinitiou 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, 

 Cryptoculijle, and Scaphauucephalus : — " Body distinctly 

 divided into narrow anterior part and plumper posterior 

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

 ventral sucker ; long axes of testes transverse to long axis 

 of body ; ovary globular ; windings of uterus extend laterally 

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

 That such a family as the Coenogonimidae 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 

 iniportatice. The genus Ascocotyle appears to indicate a 

 relationship with the Brachycoeliinae, and it is quite possible 

 that the latter, along with the genera Spelotremu, Levinseniella, 

 and Gijmnophallus, might be included iu the same familv. 

 The genera Tocutrema, Cryptocotijle, and Scap/ianocep/ialus, 

 Jiigersk., represent the furthest stage w hich the approximation 

 of the genital aperture with the ventral sucker has reached. 

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

 Tocotremiiice, n. stibfam., is appropriate. 



Cryptocotyle concavum (Crepl.) ? 



This form occurred very numerously in Phalncrocorax 

 yracuius ; over a hundred examples were taken from one 

 bird. The favourite habitat is the anterior part of the 

 intestine and tlie duodenum. Distomum coitcavuni has been 

 rccordctl by several observers from a large number of hosts. 

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

 and he was the first 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, l)eing 

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

 slightly shorter than the pharynx, and thus much shorter 



