8 PROCEEDINGS OF THE (;EOLOGICAL SOCIETY. [Nov. 10, 
son with a vertebra from the anterior dorsal region of the specimen in 
the British Museum, I can find absolutely no difference, except that 
the vertebra in Mr. Fox’s specimen is a shade smaller. The centra 
of the anterior dorsals in the former are rather less than 0-7 inch 
long; in the latter the measurement is 0°63 inch. The difference, 
therefore, is not more than =, of an inch. The vertebral column of 
the specimen in the British Museum has been particularly described 
by Professor Owen; but the caudal vertebree have been much more 
completely cleared of the matrix since his memoir was written. The 
remains of eighteen vertebree may be made out, in consecutive 
series, from the cervical to the posterior dorsal region; and the posi- 
tion of the ilium is such, that there can hardly have been more than 
two or three vertebrae between the hindermost of those which are 
visible and the sacrum. In the most anterior of these eighteen ver- 
_ tebree (which may thus, probably, be the twentieth, or twenty-first, 
from the sacrum) the anterior, escutcheon-shaped, face of the cen- 
trum is distinctly convex from side to side, and slightly concave from 
above downwards, while the posterior face is markedly concave. The 
neuro-central suture passes through the capitular process; and the 
tubercular process springs much higher up upon the arch, beneath 
the preezygapophysis, the articular face of which looks as much in- 
wards as upwards*. It is only the hindermost, or ninth, cervical 
vertebra of a crocodile which presents these characters. In all 
the more anterior cervicals the neuro-central suture passes above 
the process for the capitulum of the rib; I therefore conclude that, 
in all probability, the anterior vertebra of the Hypsilophodon ske- 
leton belonged to the posterior region of the neck. I should think it 
very possible that there may have been seven, or eight, cervical ver- 
tebree between the most anterior of those preserved and the head. 
In this case, the light head, borne upon the relatively long neck, 
will have given the fore quarters of Hypsilophodon much resem- 
blance to those of a Monitor. 
Professor Owen concludes, from certain striz on the articular 
surfaces of the vertebral centra, that ‘the vertebral bodies of the 
Iguanodon were coarticulated by means of an intervertebral ligament, 
as in the class Mammaha;” and he emphasizes this conclusion by 
putting it in italics. Ihave little doubt that the vertebral centra 
of Hypsilophodon were so connected ; but so are those of a Crocodile, 
and the fact does not constitute the slightest evidence in favour of 
the mammalian affinities of the Dinosauria. 
In resuming my study of the specimen of Hypsilophodon in the 
British Museum, for the purposes of the present paper, the diffi- 
eulty which had previously presented itself of reconciling what could 
be seen of the structure of the bones numbered 66 and 67 (tab. i. 
‘ Fossil Reptilia of the Wealden Formation’) with what is known 
of the tibia and fibula of the Dinosawria returned very strongly 
* The two following vertebra have similar characters ; but the articular sur- 
face of the sixth appears to be slightly concave in front as well as behind. In 
this vertebra the transverse process springs from the arch, far above the neuro- 
central suture. 
