PARASITES OF A CHAPMAn's ZEBRA. 443 



more difficult by the similai-ity presented by the two species 

 C ylichnostomum goldi and Cyliclmostomum pseudo-catinatum, 

 Yorke & Macfie, 1919, seen in the following comparison. 



Both C. goldi and C. j^setido-catinatum are described as having 

 a small and delicate body. Boulenger gives the length of the 

 male C goldi as from 5'2-6 mm. and its maximum breadth 

 230/x-280ft (average 255ya). Yorke and Macfie found that the 

 length in ten males of C. jjseudo- catmainm ranged from 5*2- 

 66 mm., and that the maximum breadth averaged 260f-. The 

 females of C. goldi were 6-6-7 mm. in length and 280/a-300/x. 

 (average 290/^) in breadth. Ten females of C. pseitdo-catijiahwi 

 measured from 6"l-7"7 mm. in length and averaged 320/x in 

 breadth. These measurements show that the size of the body 

 of theworms of both species is practically identical. The slight 

 difference between the two species present here is not gi-eater 

 than that between the measurements of individuals of the same 

 species. 



A neck is reported to be absent in 0. goldi, but present in 

 C. pseudo-catiiiatum. In the figure of the former species, how- 

 ever, a very slight constriction in the neck region is seen. 



The mouth collar in both species is marked oft' from the rest of 

 the skin by a definite constriction. In the figures given, the 

 mouth collar, in both, is seen to be of a similar shape, being 

 rather high and almost ellijjsoidal in latei'al view. 



The submedian head papilipe in C. goldi are small and do not 

 project beyond the middle of the external leaf crown. In 

 C. pseudo-catinatmn these papillfe are larger and project beyond 

 the anterior edge of the external leaf crown. In both species 

 the submedian head papilla? are conical and their extremities are 

 not separated off by lateral notches. 



Boulenger says that the lateral head papilla3 of ('. goldi are 

 very inconspicuous, while Yorke and Macfie say that those of 

 C. jyseudo-caiinatum are prominent. In the figures, however, 

 the Ifiteral head papillfe of both species appear very similar as 

 regards size, in relative proportion to the rest of the head, and in 

 shape. 



Boulenger gives " about 20" as the ninnber of elements in the 

 external leaf crown of C. goldi, while Yorke and Macfie give 20 

 as the number of these in C. j)seudo-catinatu}». These leaves 

 are large and pointed in both species. 



The number of leaves in the internal leaf crown of C. goldi is 

 given as 30-32, and Boulenger says that these leaves are shorter 

 than those from the external corona. Yorke and Macfie only 

 say that the internal leaf crown of C pseudo-catmatum consists 

 of numerous long narrow elements. Their figure shows these to 

 be shorter than the leaves of the external corona. In both 

 C. goldi and C jyseudo-catinatum the internal leaf crown arises in 

 more than one plane. This ai'rangement is present in the othei- 

 members of this group of Cylichnostomes, i.e., C. catinatuvi and 

 C. cdveatum. 



