A ri'EliODON iMACKOGNA'l'IlUS. 
227 
condyle by a deep notch and is slightly inflected. The coronoid process is incoin[)lete. 
The dental canal (d./.) opens low down near tlu* ventral border. On the outer face of 
the mandible there are four or five foramina., of which the most anterior is beneath the 
alveolus of 1, the next beneath the middle of pm. 2, the third and fourth beneath 
the front and hinder roots respectively of pm. d. The third molar is represented by its 
alveolus only. The secoiul consists of a high anterior portion and a large talon with a 
blunt cutting-edge. The anterior portion consists of a large posterior cusp with a much 
smaller one closely united to its antero-internal side, the two together forming a very 
blunt and imperfect blade ; in Pterodon and Ilpoinodon the antero-internal cusp is 
enlarged and secant, and with the posterior cus[) forms the powerful cutting-blade of 
the carnassials. There is no trace of a postero-internal cusp. The first molar is much 
smaller than m. 2 ; it is greatly worn, particularly on its antero-e.Nternal face. The 
anterior half of the tooth is composed of a small antero-internal cusp (paracone) and a 
larger main j)osterior cusp (protocone). The talon consists of an outer cusp and a lower 
inner ridge ap})arently continuous with the cingulum. 
The fourth premolar is much larger than ni. 1 ; it is composed of a large stout main 
cusp and a small talon. The second and third ])remolars are simple com[)ressed cones, 
each borne on a pair of relatively large roots. In both premolars ami molars the 
cingulum is well marked. Pm. 1 is re])resentcd by its alv(‘olus only; it seems to have 
been a one-rooted tooth squeezed outwards between the hinder edge of the canine in 
front and pm. 2 behind. The canine is relatively large, and there are three incisors 
so crowded together that one, probably i. 2, is displaced so as to lie above and behind 
the other two. 
The dimensions (in centimetres) of this specimen are : — 
Total length of the jaw 22 
Depth of ramus at hinder end of symplly.^iN d'2 
,, „ beneath m. 3 3'2 
Length of symphysis o'S 
Width of condyle 2‘3 
Distance between hinder border of the alveolus of wi. 3 and 
the posterior angle of the condyle 10'2 
Autero-posterior diameter of canine 2 
The dimensions (in centimetres) of the cheek-teeth are: — 
Length. Width. 
«i. 3 (alveolus) la; 
m.2 TO ’SJ 
vi.l 1-2 -7 
pm. 4 1’7 1 
pm.‘d TI -9 
pm. 2 T2 '7 
M. 8880. Tlaster cast of above specimen. Made in the Briti.dL Museum. 
C. 8815. Tosterior portion of right ramus of mandible with m. 1-3 in ])crfect jtreservafion (text- 
fig. 73). The description given above of the second molar in specimen C. 8982 applies 
equally to m. 2 and m. 3 in this mandible. It can, however, be seen that the cingulum 
2g 2 
