92 TEETIAET YEETEBEATA OP THE EATtM. 



Genus MEGALOHYRAX, Andrews. 



[Geol. Mag. [4] vol. x. (1903), p. 340.] 



Hyracoids of large size. The postero-internal cusp of the posterior premolars 

 well developed, at least in pm. 4. In some species the two posterior incisors have 

 two roots. 



Megalohyrax eocaenus, Andrews. 



[Plate VI. figs. 1, 2; text-fig. 39.J 

 1903. Megalohyrax eoecenus, C. "W. Andrews, Geol. Mag. [4] vol. x. p. 340, fig. 1. 



Type Specimen. — ^Eight maxilla with the canine, premolars, and molars (PI. VI. 

 fig. 2) ; British Museum. 



The type species, in which the length of the molar and premolar series together is 

 16"2 cm., that of the molars alone 8'6 cm. 



Form. & Loc. — Fluvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 



Dentition (PI. VI. fig. 2). — The teeth are brachyodont and form a slightly curved 

 series, which, so far as the molars and premolars are concerned, is traversed from end 

 to end by a well-marked valley lying between the ectolophs of the teeth on the one 

 hand and the inner cusps on the other. 



In the upper molars the ectoloph is W-shaped, the parastyle and mesostyle being 

 strongly developed, while the metastyle seems to have been wanting except in the 

 last molar. In this tooth there is a small posterior lobe formed by the metastyle {mt.s.) 

 and hypostyle (h.s.), but it is much smaller than in SagTiatherium and the tooth is 

 consequently more quadrate in outline. Behind the parastyle and mesostyle in m. 3 

 and behind the mesostyle at least in m. 2 there are small accessory styles [ac.s.) 

 on the cingulum : these have been observed in this species only. The main cusps of 

 the ectoloph {a.e. and p.e.) are V-shaped and form no projection on the outer wall 

 of the tooth. The inner cusps are large and wear to a V-shaped surface, the anterior 

 arms of the V's running outwards and forwards to the parastyle and anterior end of 

 the postero-external cusp respectively. The cingulum is slightly developed on the 

 inner half of the anterior face and on the anterior half of the inner side of the tooth. 



The premolars are all simpler than the molars. The outer half of pm. 4 is 

 wanting, but fm. 3 is complete. Its ectoloph is composed of three elements, an 

 anterior parastyle {ps.) and a pair of subequal cusps separated externally by a slight 

 fold. On the outer side of the tooth there is a small tubercle on the cingulum, most 

 probably the mesostyle {ms.). The inner half of the tooth consists of a large antero- 

 internal cusp exactly similar to the antero-internal cusp of the molars and like it 

 giving a V-shaped surface in wear. Behind this on the extreme edge of the postero- 



