28 
Sclerostomes of the Donley 
and other additions will no doubt be made, especially to the last-named 
genus, as more material from horses and donkeys is investigated; it is however 
interesting to find an undescribed species among the larger Sclerostomes 
belonging to the genus Strongylus s.s. 
The new species from the donkey is a large form, in some respects inter¬ 
mediate between Strongylus equinus (Looss) and S. edentatus (Looss), but 
possessing some characteristic features peculiar to the species, it will no doubt 
be found not to be restricted to that host but to occur in the horse as well. 
Owing to the thickness of the head and neck muscles in the larger forms 
of Strongylus I have found the anatomy of these worms somewhat difficult 
to make out in glycerine mounts and I have found it desirable to examine 
them in a medium of rather higher refractive index. For this purpose pure 
white creasote (into which the worms may be transferred direct from alcohol 
without shrinkage) has proved very suitable. I have to thank Mr H. A. Baylis, 
of the British Museum, for calling my attention to this very useful reagent. 
Genus Strongylus Mueller 
(= Sclerostoma Rudolphi). 
Strongylus asini sp. n. 
Specific diagnosis. Strongylus : Body large, 18-42 mm. in length with a 
maximum thickness of T8-2-5 mm. 
The head (0-6-T3 mm. in breadth) is divided from the rest of the body by 
a slight constriction to form a neck-like region, similar to, but not nearly so 
well defined as that of S. edentatus. 
The mouth is circular and of considerable size (320-470 g, in diameter). 
The mouth collar is deep and sharply marked off from the rest of the skin. 
External and internal leaf-crowns are of the type usual in Strongylus, 
especially resembling those of S. equinus. The lateral and submedian head- 
papillae are also as in the other species of the genus. 
The mouth capsule is strongly developed, like that of S. edentatus it 
appears markedly cup-shaped when seen in a dorsal or ventral view (Fig. 1 a), a 
in a lateral view (Fig. 1 b) the dorsal wall is seen to be shorter and more> 
convex than the ventral, thus recalling the similar structure of S. vulgaris. 
The dorsal gutter is well developed but considerably shorter than in the 
other species, its anterior termination being some distance behind the anterior 
margin of the mouth capsule (Fig. 1). A single tooth arises from the base of 
the dorsal gutter, like that of S. vulgaris it is divided into two broad lateral 
projections which are however relatively much lower than in that species 1 
and subdivided by ill-defined grooves into a number of rounded cusps. The 
latter are variable in number, in the majority of specimens, however, three 
principal cusps are conspicuous (Fig. 1 a), each composed of several smaller 
ones. There are no ventral teeth such as are found in S. equinus. 
The excretory pore is situated in the head region as in S. equinus and 
S. edentatus. 
