78 Records oj tite Indian Museum . [YoL. XV, 



done by a shark, and that sharks frequently attacked and ate Hilsa 

 irom the large net. A few days later we were fortunate in catching a 

 shark in one of the small shangla jals. It proved to be a specimen of 

 Carcharinus gangeficus (Miill. and Henle), which measured a little over 

 6 feet. The stomach contained a Hilsa, partly digested, and also a 

 portion of the net. On examining, carefully, the partly digested 

 Hilsa, it was found that the flesh of this fish contained numbers of 

 club-shaped Cestode cysts, which, as a result of the partial digestion of 

 the fish, were actively emerging from the flesh into the stomach of 

 the shark. These cysts, which occurred in the muscles, had not been 

 noticed previously. The large intestine of the shark contained num- 

 bers of adult Cestodes, but the spiral valve was clean. These para- 

 sites were found, ultimately, to be of two species, viz., (1) Discoceph- 

 alum pilecUum, Linton. The only species of the genus was recorded 

 by Linton from the spiral valve of the dusky shark Carcharius ohscurus ? 

 Woods Hole, Mass., July 19th, 1886 ; it has not been recorded since. 

 (2) RhyncJiohothrins ilislia, n. sp., which forms the subject of this paper. 

 All the cysts seen emerging from the partly digested Hilsa were found 

 to contain larvae of Rhyrtchohofhrius ilislia. No cysts were obtained 

 which contained larval forms of Discocephalum fileatum, Linton. De, 

 in his report on the " Fisheries of Eastern Bengal and Assam," 

 Shillong, 1910, mentions that sharks and saw-fishes follow the Hilsa 

 up the rivers of Eastern Bengal and Assam. This is certainly true 

 of Carcharinus gangedcus. 



Systematic position. 



Family Tetrarhynchidae. 

 Sub-tribe Trypanorhyncha, Diesing. 

 Sub-family Phyllorhynchinae, Van Beneden. 

 Sub-family L Dibothriorhynchinae. 

 Family Dibothriorhynchidae, Diesing. 

 Genus Rhynchohothrius, Rudolphi. 

 {Tetrarhynchus of authors.) 



Generic characters : — Body taeniform. Neck tubular. Head con- 

 tinuous with neck, with two opposite bothria, parallel or converging 

 at the apices, lateral or marginal, entire or undivided, or, either 

 bilocular with a longitudinal partition, or bilobed or divided. Probo- 

 scides four, terminal, filiform, armed, retractile in the neck, for the 

 most part longer than the head. Genital apertures marginal, female 

 lateral, or male and female marginal approximate. ^ 



Rhynchobothrius ilisha, n. sp. 

 (Plate iv, figs. 1—7.) 

 Bothria two, lateral, entire, rounded, external face hollowed to form 

 a sucking disc ; widely separated posteriorly, and approximated ante- 

 riorly. Neck shorter than the head, flat. Proboscides filiform and 

 armed with four kinds of hooks, arranged in oblique circles, the larger 



1 After Linton (2). 



— «^ • "lui^mp^mr. 



