108 
TEETIARY VERTEBEATA OF THE FAYtM. 
(liainotcr was about 1'3 cm. The canine (Pi, VIII. fig. 1 a, c.) is also known only from 
its alveolus, wliicli is situated immediately behind and a little to the inner side of the 
sock('t of i. o, wliich it resembles both in shape and size. 
Pehind tlie canine there is a short diastema (about 2'5 cm.). The next tooth, 2 
(PI. IX. tig. 4), is roughly triangular in outline with one angle directed forwards. 
The crown consists of an outer row of cusps and a postero-internal shelf-like 
projection. The blade consists of two main cusps (a.e., closely united and 
])laced somewhat obliquely : of these the anterior (a.e.) is continued inwards as a 
transverse ridge to the inner border of the crown, where it passes into the cingulum. 
In front of these main cusps, and forming the anterior angle of the tooth, is a small 
but prominent cusp, apparently the parastyle (p.s.). Behind the main cusps also 
there is a small accessory cusp. The postero-internal portion of the tooth forms a 
broad slightly concave shelf with a raised border formed by the cingulum, which is 
well developed and crimped along the whole of the inner side of the tooth. 
The next premolar (^mi. 3) differs mainly from that just described in the presence 
of a largo antero-internal cusp (deuterocone), which (a.i.), together with the antero- 
external cusp (a.e.), forms a transverse ridge. The parastyle (p.s.) is present, as 
also is the posterior accessory cusp. In the specimen figured in PI. IX. fig. 4 the 
postero-internal shelf is much abraded, the enamel being completely worn through. 
The last premolar (pm. 4) is similar, but of somewhat smaller size than 3. 
The molars are bilophodont, each transverse crest consisting of a higher and 
somewhat pointed outer cusp and a lower, blunter and more worn, inner cusp. The 
postero-internal cusp has a tendency to be prolonged backwards into a small blunt 
lobe, which in wear gives rise to the pattern shown in m. I (Pis. VIII. fig. I a, X. fig. 2). 
This seems to be the beginning of the gradual addition of successive transverse ridges 
to the posterior end of the tooth so characteristic of the suborder. The cingulum is 
very well developed on the anterior and internal faces of the teeth. The enamel is 
marked by a sculpture consisting of numerous irregular grooves : these are especially 
marked on the cingulum, to which, in some cases, they give a beaded appearance. 
This sculpture is best developed in the molars of M. gracile, in which also the 
cingulum is especially well marked (PL XVII. fig. 3). 
Mandible . — The horizontal rami of the mandible (PI. X. figs. 1, I a) are very 
stout and massively constructed. Tlie outer face is strongly convex from above 
downwards, the inner face nearly flat. The spout-like symphysis is long and broad ; 
its ventral surface is evenly convex from side to side, while the upper surface is 
concave in the same direction and was continuous anteriorly with the up[)er surface 
of the procumbent incisors. The mental foramen (m.f.) is situated beneath pm. 3 
and somewhat nearer the ventral than the dorsal border. The thickened anterior 
edge of the very wide ascending ramus arises on the outer side of the jaw about 
opposite the anterior lobe of m. 3. It slopes somewhat forwards, and from its upper 
