228 



TERTIAEI VEETEBEATA OF THE PAYtM. 



is strongly developed on the inner side of the cutting-talon, which is slightly notched in 

 the middle. The talon of m. 1 is composed of an outer cusp, a very small posterior and 

 a rather larger inner tubercle belonging to the cingulum, the three surrounding a 

 shallow depression. The dimensions (in centimetres) of the teeth are : — 



Length. Width. 



m. 3 1-9 1 



TO. 2 1-8 -9 



TO. 1 1-3 -6 



M. 8873. Plaster cast of the above specimen. Made in the British Museum. 



M. 8437 a. Portion of right ramus of mandible with greatly worn and broken cheek-teeth. 



M. 8437b. Portion of right ramus of mandible with pm.2 and 3 complete, the other cheek-teeth 

 broken and worn. Figured on PI. XIX. fig. 4. 



M. 8436. Posterior portion of right ramus of mandible with m. 2 and m. 3. Figured on PI. XIX. 



Text-fig. 73. 



fig. 5. 



Portion of right ramus of mandible of Apterodon macrognaihus : A, from above j B, from outer side. 

 pm. 4, fourth premolar ; to. 1-3, the molars. § nat. size. 



The following specimens are referred provisionally to this species : — 



M. 8439. Nearly complete axis vertebra. In this vertebra the centrum is very much depressed ; 

 anteriorly its ventral surface is concave from side to side, but posteriorly there is a median 

 keel terminating behind in a hypapophysis. The odontoid is much flattened dorso- 

 ventrally ; its ventral surface for the atlas is limited posteriorly by a sharp ridge. 

 The lateral surfaces are about as deep as wide, their ventral borders being produced 

 downwards considerably below the ventral surface of the rest of the centrum. The 

 backwardly directed transverse processes are large and long, extending considerably 

 behind the posterior end of the centrum ; the vertebrarterial canal is small. The neural 

 canal is both wide and high. The neural spine is a very high hatchet-shaped plate 

 projecting considerably backwards behind the rest of the vertebra ; its postero-ventral 

 border is much thickened. The posterior zygapophyses are massive projections, their 



