112 
TEETIAliY VEllTEERATA OF THE FATtJM. 
])ro(lucc(l l)ackwar(ls in tlie middle line into a blunt hypapophysis and bears on its 
upper surface a fairly well-defined surface for the odontoid process. 
In the axis (PI. XI. fig. 2) the neural spine {n.sp.) is high and directed backwards ; 
its shar]) anterior border is convex and the thickened posterior border bears a deep 
fossa for tlie attachment of ligaments. The neural canal is high and its floor broad 
with a median elevation, which is continuous anteriorly with the upper surface of the 
odontoid. This process (o.rZ.) is relatively large, somewhat laterally compressed, and 
bears on its ventral surface a well-defined surface for articulation with the atlas. From 
the hinder border of the odontoid a hsemal ridge runs back along the centrum and deepens 
and widens considerably posteriorly, so that the hinder articular surface of the centrum 
is much deeper than broad and is produced downwards into a sort of haemapophysis. 
'i’he slightly convex surfaces for articulation with the atlas project laterally beyond 
tlie rest of the centrum to a considerable extent. Near the posterior border of the 
centrum there is a small transverse process perforated by the vertebrarterial canal ; 
the small upper pedicle rises from the base of the neural arch, the larger ventral one 
from the centrum. The posterior zygapophyses {p.z.) are oval in outline. 
The rest of the cervical series is not completely known. In the middle cervicals 
(f 3rd or 4th, PI. XL fig. 3) the centrum is relatively short; its articular ends are 
slightly concave in the middle, with a broad thickened border ; and the concavity 
is greatest on the posterior surface. There is a slight Inemal ridge which deepens 
somewhat behind. The neural spines {n.sp.) are short, pointed, and backwardly 
directed processes. The large transverse processes are perforated at their base by a 
canal {v.c.) and are bifid at their extremities, the upper process being very small 
and directed upwards, the lower forming a large downwardly directed flange. The 
zygapophyses are very large. The posterior cervical differs from that just noticed 
in the fact that the spine is higher, while the downwardly directed flange is greatly 
enlarged and has a thickened ventral border. In the anterior dorsals (PI. XI. fig. 4) 
the centrum is short, the anterior articular surface is oval and concave in the middle, 
while the posterior surface is also oval and slightly concave ; externally it passes into 
a pair of facets {c.f.) for the heads of the ribs. There is a haemal ridge. 44ie 
transverse processes {t.p.) are short and stout : on their outer ends there is a deeply 
concave facet {t.f.) looking outwards and downwards for the tubercle of the rib. The 
neural spine is a high, pointed, and backwardly directed process. 
A nearly complete vertebral column (C. 10005), associated with a very imperfect 
skull, was collected from the Middle Eocene beds, and has already been mentioned as 
undoubtedly belonging to a species oi Mwrithermm, |)ossibly even to a large individual 
of M. hjoasi. Considering both the size and some differences in details of structure 
in such vertebrae as can be compared, it seems advisable to refer to this specimen 
as Mmritlierium sp. until sufficient evidence is available either to justify regarding it as 
belonging to a new species or definitely relegating it to M. lyonsi. The vertebrae 
