322 ME. G. S. WEST ON A NEW SPECIES OE DISTOMUM. 



yyOn a New Species of Distomum. By Gr. S. West, A.E.C.S., 

 Scholar of St. John's College, Cambridge. (From the 

 Biological Laboratory, Eoy. Coll. Sci. London.) (Com- 

 municated by Prof. Gr. B. Howes, Sec. Linn. Soc.) 



[Bead 6th June, 1895.] 



(Plate XI.) 



Whilst dissecting the head, of Fhilodryas ScTiottii (one of the 

 Opisthoglyphous Colubridse), some dozen or more specimens of 

 a small species of Distomum were observed in the buccal cavity 

 and several more in the narial cavity ; the narial passages were 

 also full of eggs. On careful examination and comparison with 

 descriptions and figures of published forms, it proves to be an 

 undescribed species which I designate as follows : — 



Distomum Philodetaditm, n. sp. 



Body fusiform, broadest in the middle, tapering to each end, 

 anterior oral extremity rounded, posterior caudal extremity more 

 or less pointed ; epidermis closely beset with very minute spines, 

 which are much fewer posteriorly ; oral sucker orbicular, almost 

 ventral in position ; ventral sucker sessile, situated at about one 

 third the length of the body from the anterior end, orbicular, and 

 of the same size as the oral sucker. Intestine simple, oesophagus 

 extremely short, branches long and narrow, reaching almost to 

 the extremity of the tail. Genital pore posterior to the ventral 

 sucker and a little to the left of the median line. Length 

 3-5 mm. ; breadth 0*8-l"3 mm. Eggs numerous, very minute, 

 length 0*03 mm., breadth O'OIS mm. 



The snake from the mouth of which this Trematode was 

 obtained is a Brazilian one. Curiously enough, two other species 

 described as infesting the buccal cavities of snakes are also 

 S. American. These two species are D. Boscii, Cobb. (" On 

 some new forms of Entozoa," Trans. Linn. Soc. vol. xxii. 1859, 

 p. 364, t. 63. f . 67), and D. incerta, Cobb. (" Notes on Parasites 

 collected by the late Charles Darwin," Journ. Linn. Soc. vol. xix. 

 1885, pp. 177-178, and iig.), Erom both these species it differs 

 in its external form, its larger ventral sucker, in the shortness of 

 its oesophagus, and in the position of the genital pore ; moreover, 

 D. Boscii has a much smaller oral sucker, and D. incerta is quite 

 smooth. The dimensions of Z). ^hilodryadum and also of the 



