MCERITIIERIUM. 
99 
Suborder PROBOSCIBEA. 
Bones of skull, particularly those of the cranial region, with a strong tendency to 
the great development of the diploe ; an alisphenoid canal ; no condylar foramen. 
Molars lophodont, passing from a bilophodont, brachyodont type in the earliest forms 
to a very hypsodont condition with numerous transverse crests in the later. Second 
upper incisors enlarged to form tusks. Feet, where known, pentadactyl and digiti- 
grade with taxeopod structure: a centrale in the carpus, at least in the young. No 
entepicondylar foramen in the humerus. Radius and ulna, tibia and fibula complete 
and separate from one another. No third trochanter in the femur. Astragalus 
articulating distally with the navicular only. Calcaneum with large fibular facet. 
Family MGERITHERIID.F:. 
Comparatively small animals about as large as the Tapir. Skull with greatly 
elongated cranial region, the orbits being placed far forwards and the nares nearly 
terminal ; probably a small proboscis was present. More than one pair of incisors 
in upper and lower jaws : molars quadritubercular and bilophodont. 
Genus MCERITHERIUM, Andrews. 
[Tageblatt des V. Internationalen Zoologen-Congresses, No. 6, p. 4, Berlin, 1901 
(Verhandlungen, p. 528).] 
Dental formula : — i. | ; c. ^ | ; m. 3 . 
The second incisors in both jaws greatly enlarged and tusk-like. The last premolar 
not bilophodont ; molars bilophodont. 
This genus is represented by several species, of which Mcerithermm lyonsi is the 
type. It is found in both the Middle and Upper Eocene deposits of the Fayum. 
Skull (PI. VIII. ; PI. IX. fig. I ; PL X. figs. 3, 4 ; text-fig. 40). — The following 
description of the skull is founded mainly upon a nearly complete specimen (PI. VIII. ; 
PI. IX. fig. I) belonging to a young individual, in which the second incisors and third 
molars are still uncut. This skull (C. 7867) is from the Upper Eocene beds, but does 
not seem to differ in structure from the less nearly perfect specimens from the Qasr-el- 
Sagha beds (Middle Eocene). In some cases references will be made to some of 
these other specimens wdien they supply more satisfactory information on any point. 
In its general form the skull is long and somewhat depressed, wffth very strong and 
o 2 
