NEGATOR 



457 



Contains the following genera : (i) Bunostomum (= Monodontus) ; 

 (2) Necator ; (3) Bathmostomum ; (4) Gaigeria. 



Genus. Necator, Stiles, 1903. 



Mouth capsule small, narrowed anteriorly (ventrally) by chitinous 

 plates, as in Uncinaria. On each side of the base of the dorsal cone 

 a lateral chitinous plate or lancet with smooth edge (not serrated), 

 ventral lancets as in Ancylostoma. No ridges on outside of ventral 

 wall. Aperture of dorsal cesophageal gland on tip of a cone pro- 

 jecting freely into the buccal capsule. Bursa closed. Posterior ray 

 cleft to its root. 



Necator americanus, Stiles, 1902. 



Syn. : N. africanus, Harrison, 1910. 



Male 8 mm. long, female 10 mm. The head is strongly bent dorsal- 

 wards so that almost by this character alone it can be distinguished 

 from Ancylostoma duodenale. The buccal capsule is markedly small 



FIG. 334. Necator americanus. Showing cutting plates and the projecting 

 dorsal ridge, and deep in the cavity the edges of the ventral lancets, x c. 475. 

 (After Looss.) 



in the male, 0-093 by 0-084 mm., in the female o'li by 0-097 mm. 

 There are no teeth anteriorly on the ventral side of the capsule, but 

 instead there are two cutting chitinous plates, the anterior portions 

 of which are prominent and angular, and meet in the middle line 

 in front. Posteriorly on each side the plate projects less, while 

 between the anterior and posterior parts there is a deep angle. The 

 inner (posterior) ventral lancets which also occur in A. duodenale are 

 large, and project far into the lumen, the tips of these, of the lateral 

 lancets, and of the dorsal cone almost meeting in the centre of the 

 lumen. As already stated in the definition of the genus Necator, there 

 are also lateral lancets which start from the base of the dorsal cone. 

 This dorsal ridge, or rather in this case cone, is a striking object in 



