354 T'ransactions.— Geology. 
articular surface is, moreover, displaced obliquely backwards with reference 
to the general axis of the vertebral column. Surrounding the ball end of 
the vertebra is a very distinct capsular ridge and groove. The neural 
arches are continuous with the anterior portions of the centra, and articulate 
by bold transverse processes, the anterior being the longer in each case. A 
slight overhanging continuation of the anterior margin of the spine over the 
. neural canal seems to indicate a rudimentary zygosphene. 
The ribs appear to have articulated with a rough surface, placed on the 
anterior and upper part of the centra. A few fragments of ribs are preserved, 
and show the articular head to have had a convex surface. The inferior 
two-thirds of the circumference of the centra presents an even striated surface, 
The centra are compressed laterally, but not constricted; length 4 inches, 
height 3:5 inches, transverse diameter of anterior articular surface 3:5 inches, 
posterior about 3 inches. The ribs, which are 1:5 inches wide, are flattened, 
and only slightly expanded at their insertion. 
The paddle bones are very remarkable, and differ altogether from anything 
else in the collection. The humerus is extremely short in proportion to its 
width, having a flattened form, and strong irregular much-recurved anconal 
processes. Its length is 6 inches, proximal width 3 inches, distal width 6 inches, 
-Radius 4:5 inches in length, 3:5 at the distal extremity, and 2-5 in the middle. 
The carpals are remarkably thin and flattened, their borders being raised and 
roughened. Only a few fragments of phalanges are preserved, from which they 
appear to have been rather elongate cylindrical bones expanded at both ends. 
The head is preserved in two portions from the orbit forwards, but a part 
is wanting in the middle. The orbital width is 7 inches, and the total length 
was about 24 inches; the length of the tooth series 14 inches. The form 
of the symphysial surface uniting the two rami, and the angle of divergence 
which they show, would make the gape about 7 inches wide, or about half the 
length of the tooth series. The teeth are badly preserved, but consisted of a 
thin layer of enamel enclosing a widely conical cavity, not constricted at the 
base. The teeth are finely striated, only slightly compressed, and without 
any well-marked ridge; length, 1 inch, greatest diameter at base ‘8 inch. 
Although firmly imbedded in cement they appear to have been attached by 
thin bases to the inner side of the floor of the dental groove, the exterior 
parapet being very low, so that the teeth must have been set in the jaw with 
a marked lateral divergence, and not placed vertically as in Leiodon. This is 
shown in two sections of the jaw.on Plate XXVL, figs. b and е, but in 
which the lines xv are perpendiculars, the drawings having been wrongly 
placed on the stone. By working out the base of the skull, which is much 
fractured, a smaller and more cylindrical tooth was exposed, which was 
probably a pterygoid tooth, such as are found in Mosasaurus. The crani 
