THE NEMATODE FAMILY GNATHOSTOMID^. 249 



Key to Species of S'piroxys. 



A. Lobes of the lips unarmed S. contorta. 



B. Each of the three lobes of each lip carries close to 



either edge of its inner surface a sharp cuticular tooth. S. gangetiea (p. 261). 



1. Spiroxys contorta* (Rud., 1819). (Text-figs. 1-3; PI. I. 

 figs. 1-4 ; PI. II. fig. 5.) 



Spirojitera contorta Rudolpbi (1819, pp. 25 (fe 242). 

 Spiroxys contorta Schneider (1866, p. 125). 



V. Linstow (1909, p. 58, figs. 22 a, 22 6). 

 Spiroxys contortits Railliet and Henry (1916, p. 114). 

 % Spiroxys contortus (Rud.) Seurat (1918, p. 23). 

 'i.Ascaris testudinis Rudolphi (1809, p. 193; 1819, pp. 25 & 



242). 

 % Physaloptera contorta Leidy (1856, p. 53). 



We have examined two sets of specimens of this nematode 

 belonging to the collection of the British Museum (Natural 

 History), one from Siebold's collection (which had been removed 

 from the stomach of Emys orhlcularis \E. europ(jea\ ) small, 

 without eggs, and presumably immature ; the other mature 

 and labelled "from a water tortoise." They have no specific 

 differences. 



The worms are much twisted. Schneider describes the body 

 as being always bent towards the ventral aspect. This appears to 

 be at least usually the case, many of our specimens having an 

 elbow-like bend in the neck-region. The head end (PI. I. 

 figs. 1 & 2) is very slender. Thence the diameter of the body 

 gradually increases, nor does it again diminish till close to the anus. 

 Except for characters common to the genus the lips are unarmed. 

 In dorsal (or ventral) view (PI. I. fig. 1) the tip of the doi-sal 

 (or ventral) lobe, particularly its pulp, is hooked posteriorly, 

 while its anterior edge is rounded off. 



In the male the caudal alse (PI. I. figs. 3, 4 ; PI. II. fig. 5) are 

 well-marked ; the amount of their distension, and of that of the 

 ventral cuticle between them, varies, but there appears to be 

 regularly a considerable swelling of the latter just before the alas 

 cease anteriorly (PL II. fig. 5). The ventral papillse a,re sessile 

 (PI. I. fig. 3). The spicules (PI. I. figs. 3, 4; PI. II. fig. 5) are 

 long, slender, tapering, and transversely striated, have the ap- 

 pearance of being hollow, and end in a very fine point (text-fig. 1). 

 They do not carry alee, aa was supposed by Schneider. 



In the female the ventral caudal notch is relatively coarse 

 (text-fig. 2). The female organs (text- fig. 3) have the generic 

 characters. 



In introducing the name Spiroptera contorta, Rudolphi (1819) 

 mentions it as synonymous with Ascaris testudinis. He had 



* For specific diagnosis, see p. 251. 



