TREMATODES OF AUSTRALIAN BIRDS. 225 



and very thick shelled. The eggs differed in size a little 

 according to their position in the uterus, the smallest 

 measuring 0*037 x 0*021 mm., the largest 0*043 x 0*026 mm., 

 while the average of all those measured was 0'039 x 

 0*023 mm. 



Comparing it with forms previously known, this species 

 seems to be nearly related to Lyperosomum lobatum, Raill. 

 from Pica caudata, and to an unnamed species in von Lin- 

 stow's collection, figured by Braun in (10 ' flg - 66) . The latter 

 is a parasite of Corvus corone. 



Lyperosomum megastomum, sp. n. (Pig. 15). 



Diagnosis, — Form elongated, cylindrical. Suckers very 

 large, wider than the body, oral smaller than the ventral. 

 Testes large, approximately equal, close together, a short 

 distance behind the ventral sucker. Genital pore in front 

 of intestinal fork; cirrus sac lying mainly anterior to the 

 ventral sucker, ovary oval, half as large as testes, long 

 axis transversely placed. Yolk glands consisting of few, 

 large follicles, occupying a short field behind ovary; uterus 

 very extensive, filling up posterior two-thirds of body. 

 Eggs large, 0*038 x 0*023 mm. 



Host. — Crested tern, Sterna bergii in the intestine. 

 Locality: Tuggerah, N.S.W. 



Type specimen in the Australian Museum, Sydney, No. 

 W. 439. 



The most striking character of this species is the size of 

 the suckers which considerably exceed the narrow cylin- 

 drical body. The worms are about the same length as L. 

 parvum (3*68 mm. on the average) but are much more 

 slender, being only 0*194 mm., in breadth at the level of 

 the testes, and 0*145 mm., in the region of the uterus. 

 Both the suckers exceed this breadth in their diameter and 

 so project beyond the lateral edges of the body. The oral 



O— December 6, 1916. 



