224 Mr. H. A. Baylis 07i the 



Nigeria. The last-mentioned specimens were kindly given 

 to me, for the purpose of comparison, by Dr. J. H. Ash- 

 worth, of Edinburgh, who Informed me that they had been 

 determined as T. tiara by Dr. B. T. Leiper*. 



It would appear, from this list of hosts, that T. tiara Is 

 not confined to the monitors (Farawws), but may also infect 

 snakes of semi-aquatic habits. That the genus, at all events, 

 certainly does so is shown by some specimens which recently 

 came to light in the British Museum collection. Having occa- 

 sion to examine the types of Balrd's species Ascaris ohconica, 

 from the Brazilian fresh- water snnke Helicops [U^'anops] angu- 

 latus, I was struck by the fact that some of the specimens so 

 labelled were distinctly smaller than others, and of a different 

 shape, especially in the region of the tail. A closer examina- 

 tion soon showed that these smaller specimens undoubtedly 

 represented a species of Tanqua. Tiiey have a very close 

 resemblance in ail respects to the type-species, but differ 

 sufficiently from it, especially when the geographical distribu- 

 tion is taken into account, to be regarded as representing a 

 distinct species. 



The genus Tanqua, as has been pointed out by Leiper 

 (1908), possesses certain features which indicate a close 

 relationship with Gnatlio stoma, Owen. He places it pro- 

 visionally in the family GnathostomidEe, and there seems to 

 be no objection at present to this classification. 



1. Tanqua tiara^ (v. Llnst.). 



Ascaris tiara, von Linstow, 1879, p. 320 ; Parona, 1808, p. 114. 

 C'tenocephaltis tiara, von Linstow, 1904, p. 102; PI. ii. f]gs. 23-27. 

 Tanqua tiara, R. Blanchard, 1904, p. 478 ; Leiper, 1908, p. 189. 



Von Linstow has given (1904) a fairly complete and 

 accurate account of this species ; his figures, however, are 

 somewhat too diagrammatic, and calculated to be misleading. 

 There are one or two points in which, after examining a 

 number of specimens, I must differ froQi him. He states 

 (1904, p. 102) that the dorsal lip has three rounded projec- 

 tions, while the ventral lip has four similar processes, inter- 

 digitatlng. Li a cleared specimen, viewed in horizontal 

 optical section, it might quite easily be imagined that this 

 was a correct interpretation of the structure. By rolling the 

 specimen over, however, under a cover-glass, in such a way 

 that first one lip and then the other can be focussed separately, 



* Since writing this paper, 1 have received several furtlier examples of 

 T. tiara from a species of Varanus in Zanzibar. 

 t For generic and specific diagnoses see below (p. 230). 



