A NEW SPEUIES OF CESOPHAGOSXOMUM. 461 



24. A New Species of (Esophagostomum (QEsophago- 

 stomum xeri, sp. n.) from n Rodent (Xerus setosus). 

 By II. J. Ortlepp, M.A., Research Assistant, Helmin- 

 thological Dept., Ijondon School of Tropical Medicine \ 

 Hon. Parasitologist to the Society. 



[Received March 9, 1922 : Read April 25, 1922.] 

 (Text-figures 1-6.) 



In Janviary 1922, I collected a number of ISTematode parasites 

 from the caica of two Bristly Ground Squirrels (Xerus setostis) 

 which had been received from South Africa, a month previously, 

 by the Zoological Society, Regent's Park, London. These parasites 

 comprised 11 males and 17 females. They were irregular] v 

 distributed in the ctecal contents. 



In the specimens, which were all killed by immersion in hot 

 70 per cent, alcohol, the anterior end of the body is bent ventral- 

 wai'ds in the form of a hook. 



The caticle is transversely striated, the distance between the 

 most anterior strite being slightly over 7 /x ; this distance increases 

 posteriorly until a maximum of 27 /a is i-eached at about one- 

 seventh of the total length of the worm ; after this the distance 

 gradually diminishes, so that in the middle of the body it is 12 u 

 and at the hinder end 7ju. 



A mouth collar (text-figs. 1 & 2) is present ; this is broad 

 and shallow, its depth being less than hall its breadth. Immedi- 

 ately behind it thei'e is a well-marked vesicular swelling about 

 as long as it is broad, but sometimes slightly longer than broad 

 (text-fig. 1). Transversely it shows fine cuticular striations. It 

 is terminated behind at a distance of about 220^ from the 

 anterior end by a cervical constriction of the cuticle ; this con- 

 striction almost encircles the worm except for a short space on 

 the dorsal surface. 



Two cervical papillce are present ; these are small, and are 

 situated behind the middle of the oesophagus at about the 

 anterior margin of the posterior third of the oesophagus. 



There are no lateral alee. 



The females are slightly longer and thicker than the males,, 

 measuring on an average 15 mm. in length, the smallest being 



13 mm. and the largest 16-5 mm. long. In the males the average 

 length is 13 mm,, the smallest being 12 mm. and the laig-est 



14 mm. 



The females have their maximum breadth at the junction of 

 the posterior and middle thirds of the body, and this breadth in a 

 female 16 mm. long is 510//. From this point the body tapers 



Proc. Zool. Soc— 1922, No. XXXI. 31 



