354 Transactions. — Geology. 



articular surface is, moreover, displaced obliquely backwards with reference 

 to the general axis of the vertebial 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 

 neiiral canal seems to indicate a rudimentary zygosphene. 



The ribs appear to have articulated with a rough surfece, 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, ai'e 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 aj)pear 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 XXVI., figs, b and c, but in 

 which the lines XY are perpendiculars, the drawings having been wrongly 

 placed on the stone. By working out tlie base of the skull, which is much 

 fractured, a smaller and more cylindrical tooth was exposed, whicli was 

 probably a pterygoid tooth, such as are found in Mosasaurus. The cranial 



