330 Proceedings of the British Association. 
and-socket articulation of the vertebre, but with the position re- 
versed, to which the name Streptospondylus has been given by 
Von Meyer. It has been found in the lias near Whitby, and the 
oolite near Chipping Norton. Prof. Owen next proceeded to de- 
scribe the remains of some gigantic Saurians, ranging from the 
greensand to the volite, and which rivalling the modern whales in 
bulk, may be presumed to have been of strictly aquatic, and prob- 
ably of marine habits.. They have the biconcave structure of the 
vertebrz, and the long bones show no trace of a medullary cavity. 
Of the first of these, named by Prof. Owen, Cetiosaurus, (de- 
scribed in report of Proc. Geol.,,Soc.) the vertebra and other bones,. 
found in the lower oolite of Chipping Norton, belonged probably 
to an individual forty feet in length. Prof. O. has assigned to 
this species the name of C. hypodlithicus ; and to another species 
the name of C. epiodlithicus, remains of which, including a ver- 
tebra eight inches in length of body, and nine inches in trans- 
verse diameter, occurs in the Yorkshire oolite at White Nab. 
The ninth section of the Report was devoted to the description 
of a large marine Saurian, teeth of which were frequent in the 
chalk of Barnwell, and in Sussex, in the Folkstone galt, and the 
lower greensand near Maidstone. From the structure of the 
teeth, Prof. O. had assigned to it in his ‘ Odontography,” the 
name of Polyptychodon. Several bones of a gigantic Saurian, dis- 
covered by Mr. Mackeson in the greensand quarries near Hythe, 
were considered as probably belonging to the same genus. Of 
the genus Mosasaurus, only a few vertebrae have been found in 
the English chalk formation. Teeth, resembling those of the 
Mosasaurus, but differing in the elliptic form of the base of the 
crown in a transverse section, have been found in the chalk of 
Norfolk, and were described by the generic appellation, Leiodon. 
The report next proceeded to the account of the extinct species, 
which manifested, in the enduring parts of their organization, an 
intimate relationship with the numerous and varied tribes of the 
smaller and lower organized Saurians: of the present epoch, to 
which the term Lacertians or Squamate Sauria were applied. 
Prof. O. observed that in this, as in the foregoing divisions of the 
Saurian order, the ancient world possessed very singular and also 
very gigantic species, which have now utterly perished, and have 
given place to carnivorous and herbivorous quadrupeds of more 
active habits and higher organization, The first. fossils noticed, 
