242 



The annulations, though very minute and closely arranged, 

 are readily visible under the high power. The cloaca lies 

 at '06 mm. from the tip of the tail. The nerve-ring is situ- 

 ated at '13 from the mouth. The oesophagus has a width of 

 •018 mm., increasing to '025 mm. 



The alae are very narrow. There are four pair of peri- 

 anal papillae, the first, second, and fourth pairs being large, 

 the third quite small and situated rather inwardly from the 

 remainder. The postanal pair are very prominent and there 

 seems to be a tiny pair inwardly from, and just behind, them. 

 There is a pair of large caudal papillae, very close together. 

 The spicules are of the usual Onchocerca form, measuring 

 '240 and '057 mm. in length, and '006 and '009 mm. in width, 

 respectively (fig. 11). 



Ransom (1920, 1921) sated that 0. lienalis is common and 

 widely distributed in the United States* It appears to be 

 a parasite of no economic importance. 



Onchocerca gibsoni, Cleland and Johnston, 1910. 

 Figs. 1, 5, 12, 15, 24. 



The common worm-nodule producer O. gibsoni, occurring 

 in cattle in Queensland, New South Wales, and the Northern 

 Territory, has been described so often that there is little need 

 to do more than call attention to a few points in structure 

 in order that they may be compared with similar parts in 

 the other two cattle-frequenting species under review. Most 

 of these particulars are referred to in the accompanying 

 tables. 



O. gibsoni (female) is a much stouter parasite than the 

 other two and its spiral ridges are much more pronounced, 

 being considerably higher and with better developed promin- 

 ences along the course of the spirals. The male of O. 

 gibsoni is also a rather larger parasite, its minimum equalling 

 the maximum of O. gutturosa, and its cuticle is distinctly 

 ornamented, ridges being indicated even on the tail. 



The ridges in the female were found to be usually situ- 

 ated at from '05 to '08 mm. apart in the mid-body where the 

 diameter was about '45 mm. The maximum height was from 

 12 to 15 micra. Between adjacent ridges there could be 

 seen, in favourable preparations, two fairly well-marked 

 striae, 25 to 30 micra apart (fig. 24). 



The nerve-ring in the female figured lies at '12 to 

 "15 mm., and the vagina at *7 mm. from the anterior end. 

 Both of. these organs vary somewhat in regard to their posi- 

 tions in relation to the anterior end. 



