168 TEETIAET VERTEBEATA OF THE EATtTM. 



M. 8892. Plaster cast o£ the above specimen. Made in the British Museum, 



C. 8016. Immature left tibia, imperfect at ends. 



C. 9231. Immature right tibia, rather smaller than last, imperfect at ends. 



C. 8334. Left astragalus, the proximal articulation of which agrees with the distal articulation of 

 the tibia just described. This bone is figured (text-fig. 59) and is very similar to 

 that described above (p. 149) and figured (text-fig. 52). It is chiefly remarkable 

 for the prominence of the knob forming its poste'ro-internal angle. The dimensions 

 (in centimetres) are : — 



Width of tibial surface, including facet for internal malleolus . 5-8 



„ calcaneal surfaces 5'6 



„ navicular surface 5 



M. 9237. Plaster cast of the above specimen. Made in the British Museum. 



C. 8636. Left astragalus, similar to last. 

 M. 8406. Left astragalus, similar to last. 



PalsDomastodon minor, Andrews. 



[Plate XIV. figs. 1, 1a; and text-fig. 50 D.J 

 1904. Palceomastodon minor, C. W. Andrews, Geol. Mag. [5] vol. i. p. 115. 



Type Specimen. — Portion of the right ramus of the mandible of a young individual 

 (PL XIV. figs. 1, 1 a) ; British Museum. 



This species is not only much smaller than P. headnelli and P. wintoni, but differs 

 in the structure of its molars, particularly of m. 3. This tooth is long in proportion 

 to its width ; it consists of three complete transverse main crests and a small talon- 

 like fourth ridge consisting of several small cusps. The anterior crest is composed 

 of two large cusps, the outer of which is connected with a small accessory tubercle 

 partly filling the first valley. The second and third crests consist of two main cusps, 

 each partly divided into two transversely arranged tubercles ; there is no tubercle in 

 the posterior main valley ; the whole tooth is more clearly lophodont than in the 

 other species. This tooth is easily distinguishable from the last molar of P. parvus, 

 which consists of only two crests and a talon, which is composed of two large cusps 

 (see text-fig. 50 C). 



M. 1 and m. 2 are both trilophodont ; the antero-external cusp in each is. connected 

 posteriorly with a small cusp in the anterior valley ; the second outer cusp is 

 distinctly divided into two tubercles, especially in m. 2. 



Pm. 4 is bilophodont, pm. 3 a simple compressed cone with small anterior and 

 posterior cingular ridges. The length of the symphysis is unknown. 



Form. & Log. — Fluvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 



