94 
TERTIATIY VERTEBRATA OF THE FATOM. 
thin alveolar border. About 2-5 centimetres behind the large tooth are two small 
alveoli for a double-rooted incisor (/. 2), and behind this again the remains of another 
double-rooted tooth, the third incisor [i. 3). The presence of these peculiar double- 
rooted iucisor-tceth seems to show that the same causes, whatever they may be, which 
gave rise to a doid:)lc-rootcd ju’emolariform canine also affect the two posterior incisors, 
so that all the teeth behind the first incisor practically form a series of cheek-teeth. 
Comparison of this premaxilla and its contained tusk with the premaxilla and 
incisor of a recent Ilyracoid show that, as in Saglt atheriimi magnum, the two are 
closely similar in most respects. The presence of the two posterior incisors is just 
what might be expected in this early form, the remarkable thing being not the 
difference between the Eocene forms and recent types but their great resemblance, 
which shows that, so far as the front of the skull is concerned, the older forms were 
almost as peculiar as the modern ones. 
Among the specimens collected by Mr. Beadnell in 1903 is the cranial portion of 
a skull (text-fig. 39) which, from its resemblance to the corresponding part of the skull 
of Saghatherium antiquum, may reasonably be referred to a Ilyracoid, and from its 
size most probably belongs to the present species. 
The occipital condyles {cond.) are large and sharply truncated at their upper border. 
The foramen magnum {f.m.) is roughly quadrate in outline. Above and external to 
the condyles there is on either side a deep depression separating them from the 
strongly developed paroccipital processes which project below their level. The 
occipital surface widens out a little above the condyles and its upper border forms 
the middle portion of a high prominent lambdoidal crest, which is continued 
downwards and outwards on to the squamosal and is continuous with the upper edge 
of the zygomatic process of that bone. Just below the lambdoidal crest the occipital 
surface bears in the middle line a roughened ridge flanked by two smaller lateral 
ones ; this portion of the surface slopes somewhat backwards. Between the upper 
edge of the paroccipital process and the squamosal there is a slit-like foramen lying 
immediately beneath the lambdoidal crest; laterally and external to the slit the 
anterior hrce of the paroccipital region of the exoccipital is closely apposed to the 
posterior face of a nearly vertical ridge of the squamosal, the two limiting a 
well-marked groove. Between the just-mentioned vertical ridge and the iq)per 
border of the zygomatic process is a triangular area, at the bottom of which the 
auditory opening must have been ; the anterior border of this depression is formed by 
a prominent postglenoid process (pgl.). 
There is a strong sagittal crest (s.e.) running forwards from the lambdoidal ridge till 
it bifurcates. The temporal ridges (p.orb.) thus formed run out on to the posterior- 
borders of the supraorbital processes. The brain-case is strongly rounded and slightly 
contracted a little behind tire orbits. The frontal region (/>’.) is very broad and flat, aird 
closely reserrrbles the same portion of the skull of Saghatherium and llgrax [Procaoia). 
