MK. G. S. WEST OK A NEW SPECIES OF DISTOMUM!. 323 



eggs are intermediate between these two species. D. Barnaldii, 

 Sonsino (" Dei Distomi dello Zamenis viridijlavus, Lacep., e di 

 una fase del cielo vitale di unodi eiso," Proc. Verb. Soc. Tosc. Sc. 

 Nat. Pisa, 1892, p. 92), is also from the buccal cavity of a snake, 

 D. Philodryadum, however, differs very considerably from the 

 latter species in general form, size, position of the genital 

 pore, &c.* Of the species of I>istomum described as infesting 

 other parts of snakes, those most nearly approaching D. Philo- 

 dryadum are D. variahile, Leidy ("A Synopsis of Eutozoa and 

 some of their ecto-cougeuers observed by the Author," Proc. 

 Acad. Nat. Sc. Philad. 1856, p. 44.), and D. signatum, Dujardm 

 (' Hisfcoire naturelle des Helmiuthes ou vers iutestinaux,' Paris, 

 1845, p. 414). From the former it differs in size, form, and in 

 the ventral sucker ; but Leidy does not describe the internal 

 anatomy of his species. D. signatum is smaller, has the suckers 

 much closer together, proportionately larger eggs, and the genital 

 pore is anterior to the ventral sucker. 



The oesophagus is very short and rather wide, and the two 

 branches of the intestine appear to arise almost directly from the 

 base of the pharynx ; but the presence of an unbranched thin- 

 walled tube posterior to the latter is clearly seen in transverse 

 sections. The simple character of the intestine, the extreme 

 shortness of the oesophagus, and the characters of the oral and 

 ventral suckers place this species in Dujardin's subgenus ^racAy- 

 laimus (Dujardin, I. c. p. 407 ; cfr. Bronn, ' Klass. u. Ord. Thier- 

 Eeichs,' Band 4, Wiirm. ]). 909). 



The testes may be on opposite sides of the body, one in a 

 more anterior position than the other ; or there may be one 

 directly behind the other on the same side of the body. One 

 vas deferens is considerably longer than the other, and the two 

 unite just at the point where the duct enters the cirrus pouch. 



In those specimens in which the uterus was greatly distended 

 with eggs, the most anterior part of it reached almost as far as 

 the anterior edge of the ventral sucker. 



The genital orifice is situated posterior to the ventral sucker 

 and a little to the left of the median line ; its position is not 



* In a paper, " Brief Notes on Flukes," P. Z. S. 1893, p. 499, Sonsino 

 remarks thati>. Barnaldii m-dj prove to be D. nigrovenosum, Belliugham (found 

 in Tropidonotus natrix). This latter is well worked out by Monticelli (" Studii 

 sui Tremalodi endoparasiti," Suppl. Zool. Jahrb. 1893). 



