299 
The two other portions of bone have been crushed, but Mr. Owen 
‘states that they belong to the distal end of the tibia, the peculiar 
strongly-marked trochlear extremity of which is well preserved. 
Their relative size to the preceding bone, supposing that, specimen 
to be part of a humerus, is nearly the same as in the skeleton of the 
Albatross. There is no bird now known north of the Equator with 
which the fossils can be compared. 
Tortoise —The remains of the Chelonian Reptile consist of four 
marginal plates of the carapace, and some small fragments of the 
expanded ribs. The marginal plates are united by the usual finely- 
indented sutures, and each is impressed along the middle of its up- 
per surface with a line corresponding to the margin of the horny 
plate which originally defended it. The external edge of each plate 
is slightly emarginated in the middle. These plates are narrower 
in proportion to their length than in any of the existing marine Che- 
lonia ; and they deviate still more in the character of their internal 
articular margin, from the corresponding plates of terrestrial Che- 
lonia; but they sufficiently agree with the marginal plates of the 
carapace of the Emydes, to render it most probable that these cre- 
taceous remains are referable to that family of Chelonia which live 
in fresh water or estuaries. 
Lacertian Saurian.—This fossil belongs to the collection of Sir 
Philip Egerton ; and it consists of a chain of small vertebre in their 
natural relative position, with fragments of ribs and portions of an 
ischium and a pubis. 
The bodies of the vertebra are united by ball and socket-joints, 
the socket being on the anterior and the ball on the posterior part 
of the vertebra; and they are further proved to belong to the Sau- 
rian class of reptiles by the presence of many long and slender ribs, 
as well as by the conversion of two vertebree into a sacrum, in con- 
sequence of the length and strength of their transverse processes. 
The remains of the ischium and the pubis are connected with the 
left side of the sacrum, proving incontestably that this reptile had 
hinder extremities as well developed as in the generality of Sau- 
rians. Of these extremities, as well as of the anterior and of the 
head, there are no traces. 
Mr. Owen then proceeds to determine to which division of Sau- 
rians, having ball and socket vertebral joints, the fossil should be 
referred. In the crocodilian or Loricate group, the transverse costi- 
gerous processes are elongated, and three, four, or five of the verte- 
bree which precede the sacrum are ribless, and consequently reck- 
oned as lumbar vertebra: in the lacertian Saurie there are never 
more than two lumbar vertebrae, and those which have ribs support 
them on short convex processes or tubercles. 
In the fossil from the chalk, the ribs are articulated with short 
processes of the kind just mentioned, resembling tubercles, and they 
are attached to the sides of the anterior part of all the vertebre, 
except the one immediately preceding the sacrum. ‘These charac- 
ters, Mr. Owen says, in conjunction with the slenderness and uni- 
form length of the ribs, and the degree of convexity in the articular 
