22G 
TKRTlATiY VERTEBTIATA OF THE FAYOM. 
Apterodon macrognathus, Andrews. 
[Plate XIX. figs. 4, 5; text-figs. 72-76.] 
J’terodon macrognallm^, 0. W. Andrews, Geol. Mag. [.5] vol. i. p. 211. 
Type Specimen.— 'Lcit ramus of mandible with m. 1-2, pm. 2-4, and the base of the 
canine (text-fig. 72) ; Geological Museum, Cairo. 
'Phis species, as its name implies, is es))ecially remarkable for the elongation of 
the jaw, particularly of the post-alveolar portion. This character furnishes a further 
distinction from Fterodon, in which the mandible is comparatively short and stout. 
'The dental formula is i. 3, c. 1, 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 
flescription, yi. yaudryi differs 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. 
rtnr/., angle of mandible; r., canine; cond., condyle; df., opening of dental canal; i. 1-3, incisors; 
m. 1-3, molars ; ^)m. 1-4, prcmolars ; .y/rn., sympb 3 ’sis. | nat. size. 
of the last premolar. Apterodon (Dasyurodon) /lonheimensis, Audreac, 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 (Uj)per Eocene) : north of Birkct-el-Qurun. 
C. 8982. Left ramus of mandible witli m. 1-2, jnn, 2-4, and base of canine in sitxi. 'fypo specimen, 
described in Geol. ]\Iag. lor. cit. .<nijira-, figured in text-lig. 72. 'Pile .sympliysis Fym.) 
is d(‘ep and extended back to beneath the ihird premolar. 'I’he mandibidar ramus is 
narrow from ahove downwards and ])roportionately very long ; the ventral border is 
nearly straight. 'Phe length of the jaw ludiind the alveolus ol the last molar is very 
gix'at. The condyle (cond.) is (iylindrical and elongated from side to si<lo ; it is on 
the same level as the alveolar border. 'Phe angnlar region [any.) is separated from the 
