19LS.] T. Southwell & B. Pkashad : Indian Fish, Parasites. 349 



from the same place. On the latter occasion it was found that 

 they were quite common in T. jasciatus as well. The specimens 

 were found to be moving freely on the mesentery and were not 

 encysted. 



They are fiat semi-oval worms (fig. 1), varying in size from 

 2-8 mm. — 5-2 mm. in length by 1-i mm. — 1-8 mm. in breadth. The body 

 is compressed, with a small circular sucker {s.i.) at the anterior end, 

 and a much larger spherical sucker-like acetabulum {s.ii.) behind the 

 anterior one. The mouth-opening lies within the anterior sucker. 

 There is no pharynx. The alimentary canal is forked, the intestinal 

 caecae {Int.) reaching the posterior extrensity. These intcfctinal caecae 

 shew short lateral projections on both sides. The excretory pore {E. 0.) 

 is situated at the extreme posterior end, connected with a triangular 

 excretory vesicle {E. v.), which lies behind the genital organs. 

 The gonads lie in the middle third of the body. The testes (T) are 

 roughly pyriform structures with the margins slightly indented, the 

 anterior testis is much larger than the posterior one. From the end 

 of each of the testis the tubular vas deferns {r. d.) leads to the base 

 of the large cirrus sac (c\ s.) situated alongside the anterior testis ; 

 the two vasa deferentia here unite to form the slightly swollen vesicula 

 seminalis, which is only the beginning of the much coiled tube lying 

 in the cirrus-sac ; the end portion of this tube — the ejaculatory duct — • 

 leads into the genital atrium {G. a.). The ovary {ov.) is an ovoidal 

 structure, with entire margins, lying in between the two testes. From 

 the ovary a thin tubular oviduct after making several loops in the 

 space between the two testes, and receiving a duct from the yolk recep- 

 tacle, is continued in a straight upward course outside the anterior 

 testis, and then curves inwards to open into the uterus. The uterus 

 [ut.) which is a large structure lying in the middle line, and extending 

 anteriorly up to the lower margin of the posterior sucker (s. ^^.), is con- 

 stricted posteriorly to open into the genital atrium. The genital atrium 

 {G. a.) lies near the anterior edge of the cirrus-sac receiving in its cavity 

 the openings of both the male and the female ducts. The genital ]:)ore 

 {G. P.), or the opening of the genital atrium, lies in the middle line about 

 the middle of the animal. 



The vitelline glands (v) lie scattered on the two limbs of the intestine. 

 The vitelline duct {Vt. d.) comes from the yolk glands and is seen to be 

 formed of a number of fine branches, the ducts from the two sides meet 

 in the middle to form a sac-like yolk receptacle, which as stated above 

 opens into the oviduct. 



A nerve collar {N . C), with two nerves running posteriorly from it, 

 can be seen surrounding the alimentary canal, just before forking takes 

 place. 



The hermaphrodite nature of the worm, the two suckers, the position 

 of the acetabvdum, the situation of the ovary between the two testes 

 (which are non-digitate), the genital pore being situated posterior to the 

 acetabulum, and the intestine having short lateral projections, place the 

 worm undoubtedly in the genus Clinostomum, Leidy (4). The present 

 species, however, differs from all previously described species, and we 

 therefore name it Clinostomum piscidium, sp. nov. 



