459 
the origin of the transverse process being close to the neurapophysis 
instead of proceeding from the middle of the side of the centrum. 
In these deviations from the Cetacea, the Cetiosaurus approaches, 
the author states, the saurian order. 
Mr. Owen then describes, with his wonted minuteness and _per- 
fect acquaintance with the subject, other caudal vertebre found at 
Blisworth, but it is not possible to abridge the details. 
Among the remains discovered near Chipping Norton are eleven 
caudal vertebrze without transverse processes, and therefore assigned 
by the author to the terminal half of the tail. They progressively 
diminished in transverse diameter from five inches to two inches, 
but without losmg in equal ratio their length, which continues 
the same, or five and a half inches in the vertebra which has only 
three inches and three lines of breadth, five inches in that which is 
two inches and nine lines broad, and four inches in that which has a 
breadth of two inches. These eleven vertebre do not constitute, 
Mr. Owen shows, a regular sequence, but detached links of the ter- 
mination of the spinal column. In all the existing genera of Cetacea 
the posterior caudal vertebrze become shorter in proportion to their 
thickness, and the terminal ones are depressed. ‘The slender elon- 
gated form of the corresponding vertebre in the Cetiosaurus, is, Mr. 
Owen shows, a striking crocodilian character ; and he adds, it is im- 
portant to observe that not any of the series of caudal vertebra de- 
scribed in this paper exhibit the vertical canals or perforations of the 
side of the centrum or base of the transverse process which so pe- 
culiarly characterizes most of the cetacean caudal vertebre. 
In his comparison between the vertebre of the Cetiosaurus and 
the Poikilopleuron, Professor Owen states that the caudal vertebrz 
of the former resemble those of the latter and most other reptiles 
from strata below the chalk in the articular surfaces being slightly 
concave ; and the vertebrze of the Poikilopleuron, especially in the 
elongated and rounded form of the body ; in its median compression, 
and in the articulation of the hemapophyses to the inferior part of 
_ the vertebral interspaces, though they are larger ; on the contrary, the 
Cetiosaurus vertebre differ in their proportions, in their structure, 
as in the absence of the remarkable medullary cavity in the middle 
part of the centrum of the Poikilopleuron; in the shortness of the 
neurapophyses as compared with the centrum; and in other minor 
points, which are fully detailed by Professor Owen. 
The author then proceeds to institute further comparisons between 
the vertebr of the Cetiosaurus and other reptilia: thus he shows 
that they differ from the vertebre of the Crocodilians in retaining 
the cylindrical form of the body to the end of the tail, instead of 
being compressed and four-sided ; that there is no trace of the ver- 
tical median division which the bodies of the caudal vertebre pre- 
sent in Iguane, Anolides and other Lacertians; that they are not 
only larger than in the Megalosaurus, but relatively longer ; that 
they differ from the anterior caudal vertebre of the Iguanodon, 
which are nearly as large, in the absence of the well-marked con- 
cavity below the transverse processes, in the form of the centrum 
not being so quadrilateral, and especially in the transverse breadth 
