86 TEETIAET TEETEBEATA OF THE FATtTM. 



small and circular in section. The cheek-teeth are somewhat more brachyodont than 

 in the recent Hyraces, even than in Procavia {Bendrohyracc) dorsalis. In general 

 structure the molars are very similar to those of the species just referred to ; but, on 

 the other hand, the premolars are widely diiferent 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 Dendrohyrax 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 which 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 (^s.), being well developed. The main outer cusps (antero-external and 

 postero-external, a.e. andjp.g.) 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 preserice of a small posterior lobe formed by the metastyle (mts.) 

 and a ridge forming the hinder border of the tooth, and probably including the 

 hypostyle (hs.). 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, which 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 which has disappeared in recent forms, though the root persists. 

 In the first and second molars the metastyle is small and is crowded 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 (pm. 1-4) are all simpler than the molars ; in recent forms 

 the three posterior at least are molariform, and in the Pliocene Pliohyrax the last 

 at least is so. It is difficult to correlate the cusps in these rather peculiar premolars 

 with those of the molars. Their 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 



