92 



Records of the Indian Museum, 



[Vol.. IX, 



Excretory vessel bifurcating into two lateral branches a little an- 

 terior to vesicle, each branch running approximately parallel to 

 the intestinal ramus on its own side. Parasitic in fishes. 



Isoparorchis trisimilitubis, sp, nov. 

 (PI. viiij figs. 9-11; and pi. ix, fig. 12.) 



These Trematodes were first discovered infesting the air 

 bladder of an adult specimen of the Silurid fish, Wallago attu 

 (Bengali, Boali), caught in a freshwater tank at Bankipur, in 

 March 1912, Since then, large numbers of specimens have been 

 obtained, and every adult fish examined was found to be infected. 

 Immature forms of this parasite have since been noted to occur 

 in the flesh of the Mahseer {Barhus tor). Specimens of Wallago 

 attu occur extensively in nearly all rivers of North and North-east 

 India, and during the floods their larvae and fingerlings enter the 

 tanks via the paddy fields. The fish is exceedingly voracious. 



The following are the dimensions of a few of the parasites 

 from Wallago attu : — 



The thickness of the largest worm was '9 mm., that of the 

 smallest '2 mm. (approximately). The dimensions and thickness 

 of the worms varied a little according to the degree of contrac- 

 tion. 



The parasites were killed in an expanded condition by spread- 

 ing two drops of spirit over the surface of the body. The w^orms 

 in every case expanded. When fully expanded, they were plunged 

 into 5 per cent formalin. For the determination of the anatomy, 

 a few specimens were dehydrated, cleared in clove oil, and mounted 

 whole. A few were stained with Delafields Haematoxylin, and 

 others with Borax Carmine. I did not prepare sections, but made 

 careful dissections of the genital organs. 



External characters. — The parasites are leaf-like and of a 

 deep flesh-colour, roughly oval in shape, the posterior margin 



1 The smallest specimen obtained. 



