ECTOPAEASITIC TREMATODES. 277 



oval area, in which lie the ovary and the testis. Common 

 genital pore lying midway between the front end of the body and 

 the front end of the adhesive disc. I counted 15 penis spines, 

 which are straight and bear a wing-like process at the middle, 

 and are 0.028 mm, long ; but as their number in other species 

 is always even, I think that there are 16 in the present species. 

 Testis irregularly ovoidal, large, with lobulated margins, nearly 

 filling up the posterior half of the area enclosed by the intestin- 

 al branches. Ovary small, somewhat comma-shaped in the 

 ventral aspect, sometimes lying in the right half of the body 

 and sometimes in the left half. The oviduct arises from the 

 smaller end of the ovary and proceeds obliquely forward, and 

 opens into the uterus, which is situated directly behind the com- 

 mon genital pore. Vaginal openings lateral, without papillae, mid- 

 way between the front and hind extremities of the body proper, 

 the two vaginal canals directed almost straight across the body 

 and meeting in the median line. Genito-intestinal canal slight- 

 ly behind the vagina, on thé same side as the ovary. Vitelline 

 lobes not very numerous, separated from one another, mostly 

 confined to the lateral portion of the body, but also present in 

 the median portion behind the testis. 



Here it may be in place to make a remark on the type 

 specimen of Leidy's Polyslomwni oblongum from the urinary 

 bladder of the food terrapin {Pseudemys rugosa), which I was 

 enabled to examine throuo'li the kindness of Dr. Stiles. At 

 my suggestion the specimen was mounted ; but it was in a rather 

 miserable condition, the hooks of the adhesive disc being all 

 gone, except those in the suckers. Enough could, however, be 

 made out to prove that the species represented by it was not 

 the P. oblongum of Wright L'^^]* There were, namely, 16 



