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ON SOME TREMATODE PARASITES OF MARSUPIALS 

 AND OF A MONOTREME. 



By S. J. JoHNsroN, B.A., D.Sc, Demonstrator in Biology, 

 University op Sydney. 



Plates Ixxv.-lxxvi. ) 



The small group of Trematodes, here under discussion, com- 

 prises two new species of Harmostomum from marsupials, and 

 two species of Mehlisia, one from a marsupial, also described as 

 new, and one from the platypus, Ornithorhynchus anatinus Shaw, 

 described by me in these Proceedings in 1901, under the designa- 

 tion Distomum ornithorhynchi{7) . The two species of Harmosto- 

 mum are closely related to one another ; but, what is more interest- 

 ing, are also closely related to //. opisthotrias Lutz, parasitic in the 

 South American marsupial, Didelphys aur it a (13) ; so nearly, in 

 fact, as I shall show in detail later on, that they must be looked 

 upon as derived from a common ancestor; and, in this way, they 

 supply some circumstantial evidence of the phylogenetic relation- 

 sliij) of the Australian and the South American marsupials. 



Harmostomum dasyuri, sp.n. 



(Plate Ixxv., Figs. 1, 5-8.) 



Parasitic in the intestine of Dasyurus viverrinus, found in the 

 vicinity of Sydney, N.S.W. 



Diagnosis. — Small, flattened worms, rounded in front, pointed 

 behind, about 6 mm. long, by 1-25 mm. broad. Integument armed 

 with spines, except on the posterior half of the dorsal surface. 

 Suckers very large, the ventral almost as wide as the body; ratio 

 of the oral to the ventral sucker^ 2 :3. Small prepharynx, well de- 

 veloped pharynx, and short oesophagus present. Intestinal limbs 

 with a forwardly directed loop, thence running back to the extreme 

 posterior end of the body. Excretory vesicle very small in its 

 unpaired part, dividing into two long branches, giving off numerous 



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