226 



TEETIAET VERTEBEATA OF THE FATt)M. 



Apterodon macrognathus, Andrews. 



[Plate XIX. figs. 4, 6 ; text-figs. 72-76.J 

 1904. Pterodon macrognathus, C. W. Andrews, Greol. Mag. [5] vol. i. p. 211. 



Type Specimen. — Left ramus of mandible with m. 1-2, pm. 2-4, and the base of the 

 canine (text-fig. 72) ; Geological Museum, Cairo. 



This species, as its name implies, is especially remarkable for the elongation of 

 the jaw, particularly of the post-alveolar portion. This character furnishes a further 

 distinction from Pterodon, in which the mandible is comparatively short and stout. 

 The dental formula is i. 3, c. 1, pm. 4, m. 3. The length of the molar-premolar 

 series is 9'7 cm., the total length of the jaw being 22 cm. Judging from Fischer's 

 description, A. gaudryi diff'ers from the present species in being smaller, in the 

 smaller size of the antero-internal cusp of the molars and of the posterior tubercle 



Text-fig. 72. 



cond. 



ang. 



Left ramus of mandible of Apterodon macrognathus, type specimen, from inner side. 



ang., angle of mandible ; c, canine ; cond., condyle; d.f., opening of dental canal; i. 1-3, incisors; 

 m. 1-3, molars ; pm. 1-4, premolars ; sym., symphysis, f nat. size. 



of the last premolar. Apterodon [Dasyurodon) Jlonlieimensis,A.\idixe&e, sp., is strikingly 

 similar to the present species, but the main cusps of the molars are rather lower and 

 blunter, and the talon is shorter. 



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



C. 8983. Left ramus of mandible with m. 1-2, pm. 2-4, and base of canine in situ. Type specimen, 

 described in Geol. Mag. loc. cit. supra ; figured in text-fig. 72. The symphysis {sym.) 

 is deep and extended back to beneath the third premolar. The mandibular ramus is 

 narrow from above downwards and proportionately very long ; the ventral border is 

 nearl)^ straight. The length of the jaw behind the alveolus of the last molar is very 

 groat. The condyle {cond.') is cylindrical and elongated from side to side ; it is on 

 the same level as the alveolar border. The angular region {ang.) is separated from the 



