86 
Ti<KTlA]{Y VEIiTEElJATA OF THE FAYtiM. 
small and circular in section. 'Hie clieck-tcetli are somewhat more brachyodont than 
in the recent Ilyraces, even tlian in Frocavia { Dendrohjrax) dorsalis. In general 
structure the molars are very similar to those of the species just referred to ; but, on 
the other hand, the ])remolars are widely different from those of all recent forms in 
being much simpler than the molars. In the following description, when comparison 
is made with recent forms, the brachyodont types like Bendrolnjrax are intended unless 
it is otherwise stated. 
The upper molars (PI. VI. fig. 6 ; PI. VII. fig. 4) consist essentially of a complexly- 
folded ectoloph and a pair of internal pyramidal cusps, from the antero-external 
angles of wdiich ridges run towards the parastyle and mesostyle respectively. These 
ridges may include rudimentary intermediate cusps, the protoconule and metaconule. 
In an advanced state of wear these ridges become continuous with the wear-surface of 
the ectoloph. The ectoloph is composed of five elements, the styles, especially the 
parastyle (ps.), being well developed. The main outer cusps (antero-external and 
l)ostero-external, a.e. and^v.c.) form projections both internally and also on the outer 
face of the ectoloph in the valleys between the styles. There is just a trace of the 
cingulum on the outer face of the tooth ; it is more pronounced on the inner half of 
the anterior face and is also present on the inner face between the antero-internal 
and postero-internal {a.i. and cusps. The last molar is the largest, its size being 
increased by the presence of a small posterior lohe formed by the metastjde (mts.) 
and a ridge forming the hinder border of the tooth, and probably including the 
hypostyle (Its.). Both the metastyle and this ridge are supported by separate roots. 
In recent Hyracoids the last molar is smaller than m. 2, owing mainly to the absence 
of this posterior lobe ; but it is interesting to notice that in most of the last upper 
molars of recent forms examined by me the hinder border of the tooth is supported 
by two or more small and evidently degenerating roots, wdiich seem to have persisted 
after the elements they originally supported have disappeared. It will be shown 
below that the same thing has happened even more clearly in the case of the last lower 
molar, the talon of wliich has disappeared in recent forms, though the root persists. 
In the first and second molars the metastyle is small and is crow'ded against the middle 
of the anterior face of the tooth behind, but there are still traces of the hypostyle 
ridge. Owing to the large size of the parastyle the molars imbricate slightly on their 
outer side. 
The upper premolars (pin. 1-4) are all simpler than the molars ; in recent forms 
the three posterior at least are molariform, and in the Pliocene Pliohjrax the last 
at least is so. It is difficult to correlate the cusps in these rather peculiar premolars 
with those of the molars. 'I'lieir ectoloph is composed of three elements, of which 
that occupying the extreme antero-external angle of the tooth seems to belong to 
the cingulum, and is equivalent to the parastyle. Behind this are two other cusps 
separated from the parastyle and from one another by furrows ; of these the anterior 
