Sclerostomes of the Horse 
T. intermedins is certainly very closely allied to T. serratus, it can 
however he readily distinguished from that species by its smaller size, 
the shape of the mouth-collar, the position of the vulva and the size 
of the eggs in the females, and by the character of the spicules in the 
males. 
Triodontophorus tenuicollis sp. n. 
Specific diagnosis. Triodontophorus: the body attains its 
greatest thickness near the middle and tapers markedly towards both 
extremities; the thickness at the level of the base of the oesophagus is 
less than half the maximum thickness. The cuticle is transversely 
ringed, near the middle and at the posterior extremity these cuticular 
rings are much as in the other species of the genus, in the narrow 
anterior region they are, however, much accentuated and modified in 
such a way as to give the body-margins a coarsely serrated appearance 
(Text-fig. 2 B). 
The head is not separated from the body and is smaller than in the 
other species, its diameter varies from 150-200p. The mouth-collar 
is depressed as in T. minor Looss; the elements of the external and 
internal leaf-crowns number 40-44. Owing to the small size of the 
head the dimensions of the mouth capsule are also much reduced, it 
has a breadth of 110—140/x and a maximum length of 70-90p. The 
anterior margins of the teeth are provided with sharp denticulations 
as in T. serratus and T. intermedins (Text-fig. 2 B). 
The oesophagus is rather short, measuring 620-900 p. The excretory 
pore is at about the same level as the cervical papillae, 680-750p from 
the anterior end. 
Female : 16-19-5 mm. in length. The maximum thickness near the 
middle of the body is 700-770p, whilst opposite the termination of the 
oesophagus it measures only 280-300 p. The body also tapers con¬ 
siderably towards the posterior end and the thickness at the level of 
the vulva is considerably less than in the other species, being only 
250-300 p. The tail region is short, the vulva being situated 460-560p 
from the posterior extremity. The anus is about 120p from the end 
of the body (Text-fig. 3 B). 
The eggs are indistinguishable from those of the preceding species. 
Male: 13-5-19 mm. in length; the greatest thickness near the 
middle is 450-650p, at the termination of the oesophagus 230-250p. 
The body also tapers towards the bursa, the breadth at the base of that 
structure being 280-350p. 
