220 
TEETIARY VEIITEBRATA OF THE FAY0M. 
Pterodon africanus, Andrews. 
[Plate XIX. fig. 3; text-figs. G9-71.] 
I'JOl’. Pterodon africanus, C. W. Andrews, Geol. Mag. [4] vol. x. p. 342, fig. 3. 
Tjjpe Specimen . — Right ramus of mandible, incomplete posteriorly, with pm. 2-4 
and m. 1-3 well preserved (PI. XIX. fig. 3) ; British Museum. 
1 Ids species is distinguished from all the others by its much larger size. 
I'vrm. cf Loc. — Fluvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 
M. 8503. bight i-amus of mandihle, wanting the posterior portion : pm. 2-4 and m. 1-3 in situ. 
Type specimen figured loc. cit. supra. 
The symphysis, which seems to have remained unanchylosed through life, is very 
deep and long, extending back to the level of the middle of pm. 3 ; its depth is largely 
due to the enlargement of the front of the jaw resulting from the great size of the canine 
tooth. Behind the symphysis the ramus increases very little in depth from before 
backwards, in which direction its lower border is gently convex. 
On the outer face of the jaw, in addition to two small apertures in the thickened wall 
of the canine alveolus (e.), there are three foramina: the smallest is in front beneath the 
posterior half of pm. 2 ; the other two {m.f.) are larger and are beneath the anterior 
lobes of pm. 3 and pm. 4 res[>ectively. 
The last molar (m. 3) is much the largest of the cheek-teeth ; it consists of a pair of 
high compressed cusps which form a cutting-blade, the posterior lobe of which is con- 
siderably the higher and has a sharp keel-like ridge on its postero-internal face ; the 
small talon apparently consists of a single cusp with a sharp median ridge. There is a 
small projection on the antero-external angle of the tooth near its base ; this seems to 
belong to the cingulum, which is wanting elsewhere. The second molar (m. 2) is similar 
to the first, except that the talon is relatively larger and forms a more distinct blunt 
edge, and the small antero-external prominence is also larger. The first molar (m. 1) is 
much the smallest of the series ; the two main cus])s, which are considerably worn, are 
less compressed and form a less trenchant blade than in the other molars. The talon is 
similar to that of m. 2 and the antero-external })rojection is almost obsolete. The fourth 
premolar (j)m. 4) is much huger than the first molar : it consists of a large, conical, 
somewhat laterally compressed and backwardly directed cusj) with a cutting-edge ; 
behind this there is a small talon also with a cutting-edge in the same line wdth that 
of the main cusp, and internal to it a sloping shelf-like surface. At the antero-internal 
and postero-external angles of the tooth there are small tuberedes belonging to the 
cingulum, which is also slightly develo])e<l along the whole inner face of the tooth, 
/'m.. .3 is similar to pm. except that the main cusp is not .so high, the talon rather 
smaller, and the antero-internal tubercle almost absent. Pm. 2 consists of a single 
cusp, of which the anterior slope is shorter than the posterior ; just a trace of the talon 
is still to he seen. Pm.\ is representeil only by its single nearly circular alveolus; all 
the other premolars and Tiiolars are implanted by two roots. Tbo alveolus of the 
canine (e.) shows that that tooth was very large and oval in section, the long axis being 
