Trematode from Protopterus. 95 



Leptodermatidae a well-marked group of parasites inhabiting 

 the mouth, lungs, oesophagus, and stomach of snakes. It 

 would seem that most of them have a preference for situations 

 more or less accessible to the outer air. It is not a little 

 striking, therefore, though probably a pure coincidence, that 

 an allied form is now found inhabiting a fish which is 

 specially adapted for breathing air. In this case, however, 

 the parasite lives in the intestine, and I have no information 

 to show that it could obtain access to the air. The relation- 

 ship, moreover, if any, between the Dipnoi and the Reptilia 

 is of the remotest character, and the presence of related para- 

 sites in both groups probably has no special significance. 



The following is a provisional diagnosis of the new 

 genus : — 



IIeterokchis, gen. nov. 



Lepodirmatidce ; with body flattened anteriorly, but much 

 swollen posteriorly, covered at the anterior end and on the sides 

 to near the posterior end with small scales. (Esophagus very 

 short ; intestinal co3ca extending nearly to the posterior end of 

 the body. A very large excretory sac is present on the dorsal 

 side, with a very wide aperture situated dorsally at some dis- 

 tance from the posterior end. Two main excretory vessels 

 present. Genital aperture situated midway between the oral 

 and ventral suckers, almost at the extreme left side of the body. 

 Cirrus-sac long and curved, containing a large vesicula 

 seminalis (divided into a non-muscular proximal portion and 

 a muscular distal portion), a small bulbous pars prostatica, 

 numerous large prostatic cells, and a long eversible cirrus. 

 Testes elongate, with entire margins ; unequal in size, the right 

 testis being considerably longer and situated farther back than 

 the left. Ovary lobate, on the right side, behind the ventral 

 sucker. A receptaculum seminis present, behind the ovary. 

 Yulk-glands occupying about the middle third of the body, 

 arranged in irregular masses along the sides. Uterus forming 

 a double sinuous loop at the posterior end of the body, and 

 having a very wide, sinuous ascending limb. Vagina running 

 nearly parallel to the cirrus-sac, long and provided with strong 

 circular muscles. Eggs 0*04 mm, in length. 



Type, H. crumenifer, sp. n. — with the characters of the 

 genus. 



Hab. Intestine of Protopterus cethiopicus : Lake Victoria, 

 Uganda. 



JSyntypes in the British Museum (Natural History). 



