140 
ti-:ktiaiiy vertejjrata of the fatCm. 
'J’ho anterior ])rcmoIar {pm. 2) is a simple, blunt, somewhat laterally compressed 
cone, of wliicli the anterior slope is much shorter than the posterior. This latter is 
worn into a broad flat surface looking slightly inwards. There are no accessory cusps, 
hut the cingulum is fairly well developed, especially on the inner side, where it is 
often somewhat crenulated or divided into small separate prominences. The next 
tooth {pm. d) consists of a larger outer and a somewhat smaller inner cusj) arranged 
transversely. There is a small postero-internal cusp, lying behind and closely 
connected with the inner main cusp : this posterior cusp may sometimes he nearly 
absent. The cingulum is well developed, especially on the anterior and posterior 
faces of the tooth, where it forms small projections. The last premolar [pm. 4) 
is a hilophodont tooth, each crest consisting of a pair of cusps — the outer higher 
and more compressed, the inner more rounded and coming into wear first. The 
inner cusps in this premolar already show a tendency towards a V -shape, the 
point of the V being turned inwards ; this form is the consequence of the presence 
of obscure and imperfectly separated tubercles on the antero- and postero-external 
sides of the inner tubercles. The anterior accessory tubercle of the front V and 
the posterior accessory tubercle of the posterior V become fused Avith the cingulum 
of the anterior and posterior ends of the tooth respectively. The other accessory 
tubercles form a bridge across the main transverse valley. The cingulum is Avell 
developed on the ends and outer side of the tooth, where it is strongly crenulated. 
The molars m. 1 and m. 2 are trilophodont, each ridge being composed of a pair 
of cusps similar to those described as occurring in inn. 4, the chief difference 
being that in m. 1 and m. 2 the posterior accessory tubercle of the last inner cusp 
is larger and, by its union with the posterior border of the tooth, forms the first trace 
of a fourth transverse ridge. The cingulum is well developed, particularly on the 
inner side of m. 2. The last molar may be said to consist of two transverse crests 
and a talon. The anterior accessory tubercles of the inner cusps are especially 
well developed. The talon consists of three tubercles, of which the innermost 
is much the largest, and the outer two are sometimes imperfectly divided. The 
crenulated cingulum is well developed, particularly on the anterior and inner 
faces. 
The above account of the upper teeth applies to specimens referred provisionally to 
P. headnelli, but Avhich may probably belong to P. wmto7u : tins applies to both 
the skull figured on PL XII. and to the upper teeth figured on PL XIV. fig. 2. 
The species being founded mainly on the form of the mandible and of the last lower 
molar, it will not be possible, in most cases, to determine the skulls and upper teeth 
with certainty till specimens have been found associated with the mandibles. 
Upper MiUc-dentUion (PL XIII.). — The ujiper milk-teeth are preserved in the 
specimen upon Avhich the account of the front of the skull is founded. In this, in 
addition to remnants of the base of the milk-incisor, there are on the left side three 
