92 
TERTIARY VERTEBRATA OF THE FATtM. 
Genus MEGALOHYRAX, Andrews, 
[G(‘ol. Mag. [4] vol. X. (1903), p. 340.] 
ITyracoids of large size. The postero-internal cusp of the posterior premolars 
well developed, at least in pm. 4. In some s])ecies the two posterior incisors have 
two roots. 
Megalohyrax eocsBnus, Andrews. 
[Plate VI. figs. 1, 2; text-fig. 39.] 
1903. Megalohyra.r eoccenus, C. W. Andrews, Geol. Mag. [4] vol. x. p. 340, fig. 1. 
Type Specimen . — Right 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 
ICr2 cm., that of the molars alone S'G cm. 
Form. & Loc. — P’luvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 
Devtition (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 parastyie 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 {li.s.), but it is much smaller than in Saghatherhun and the tooth is 
consequently more quadrate in outline. Behind the parastyie and mesostyle in m. o 
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 parastyie and anterior end of 
the postero-external cusp respectively. The cingulum is slightly develojmd on the 
inner half of the anterior face and on the anterior half of the inner side of the tooth. 
The premolars arc all simpler than the molars. The outer half of pm. 4 is 
wanting, but pm. 3 is complete. Its ectoloph is composed of three elements, an 
anterior parastyie (j)S.) and a pair of subequal cusps sei)aratcd externally by a slight 
fold. On the outer side of the tooth there is a small tubercle on the cingulum, most 
{wobably the mesostyle [ms.). The inner half of the tooth consists of a large antero- 
internal cusj) exactly similar to the antcro-internal cusp of the molars and like it 
giving a V-shaped surface in wear. Behind this on the extreme edge of the postero- 
