TICHTIAKY VKHTl'MiRATA OF THE FAYOM. 
Apterodon macrognathus, Andrews. 
[Plate XIX. figs. 4, 5 ; text-figs. 72—76.] 
11)01. I’ti'rodoii nincroijiialluiK^ 0. W. Andrews, Geol. Mag. [5] vol. i. p. 211. 
Type Left ramns of mandible witli m. 1-2, jnn. 2-4, and the base of the 
canine (text-fig. 72) ; Geological Museum, Cairo. 
This si)ecics, as its name implies, is es])ecially remarkable for the elongation of 
the jawg particularly of the post-alveolar portion. This character furnishes a further 
distinction from Pterodo)), in which the mandible is comparatively short and stout. 
'I'he dental formula is /. 3, c. 1, jim. 4, m. 3. The length of the molar-jn’emolar 
series is 0'7 cm., the total length of the jaw being 22 cm. Judging from Fischer’s 
description, A. yaudnji differs from the jU’esent species in being smaller, in the 
smaller size of the antero-internal cusp of the molars and of the posterior tubercle 
Text fig. 72. 
Left ramus of mandible of Apterodon niacroffiuiihus, type specimen, from inner side. 
anp., angle of mandible ; <■., canine ; cond., condvle ; d./'., opening of dental canal ; i. 1-3, incisors ; 
m. 1-3, molars; pm. 1-4, premolars ; .sn/ni,., symphysis, g nat. size. 
of the last premolar. Apterodon [Dasynrodon) Jlonheiniensis, AwAvqac, sp., is strikingly 
similar to the present species, but tlie main cusps of the molars are rather lower and 
blunter, and the talon is shorter. 
Form. (P Loc. — Fluvio-marinc beds (Upper Eocene) : north of Pirket-el-Qurun. 
C. 8982. ramus of maiidilde witli »>. 1—2, /nn, 2-1, and base of caniiu' in .'fitii. I’ypo .specimen, 
described in Geol. Alag. lor. rif. .‘oijiru ; ligniaMl iti t(nxt-flg. 72. I'ln^ sympliysi.s pi/ni.) 
is dee]) and ext('nd(‘d back to benealli flic third |)remolar. The mandibular ramus is 
narrow from above d<)wn\\ards and ju’oportionately" very long ; the vcmtral boiabu' is 
nearly straiglil. The length ol the jaw behind the alveolus ol the last molar is V('ry 
gia'at. The coiuhle (cond.) is (olindrieal and elongated li'om sid(' to side; it is on 
the same level as the alveolar border. I'he angrdar region {(inp.) is sejiarated Irom the 
