140 TEETIAET VEETEBEATA OP THE EATtM. 



The anterior premolar [pm. 2) is a simple, blunt, somewhat laterally compressed 

 cone, of which 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, 

 but 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. 3) consists of a larger outer and a somewhat smaller inner cusp arranged 

 transversely. There is a small postero-internal cusp, lying behind and closely 

 connected with the inner main cusp : this posterior cusp may sometimes be 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 bilophodont 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 with 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 well 

 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 pm. 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 which may probably belong to P. wintoni : this 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. 



TTpper Millc-dentition (PL XIII.). — The upper milk-teeth are preserved in the 

 specimen upon which 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 



