OPHTHALMOSAURUS ICENICUS. 67 



Basisphenoid : width 11-0 



length 8-7 



Parasphenoid : length of free portion 19'0 + 



Lac'hrymal : length of base (approx.) 12'0 



Premaxilla: length in front of anterior angle of nares ' . . . 52-0 



Articular bone : length 6'0 



Surangular (text-fig. 21) : length (approx.) 57'0 



R. 2160 (Leeds Coll. 65). Portions of the skull iucluding the basioccipital, exoccipitals, supra- 

 occipital, stapes, opisthotics, one pro-otic, quadrates, basisphenoid, portions of the roof 

 and snout ; the articulars and other portions of the mandible, some sclerotic plates ; 

 a large part of the vertebral centra including those of the atlas and axis, and of about 

 twenty-four other precaudal and sixty caudal vertebrae ; three neural arches of posterior 

 caudal vertebrce ; scapulpe, coracoids, humeri, radii, ulnae, pisiforms, carpals, and about 

 sixty other bones of the front paddles ; one imperfect ischio-pubis, femora, tibiae, fibula?, 

 and seven other bones of the hind paddles. This specimen differs in several respects 

 from the usual type and, if a second species is at any time established, it would certainly 

 have the best claims to become the type of a new form. The most striking peculiarity 

 is to be found in the quadrates, in which the posterior border above the articulation 

 instead of being merely concave is deeply notched ; on the basioccipital the occipital 

 condyle is somewhat less convex and more prolonged ventrally than in most specimens, 

 though this form is found in some skeletons with the ordinary type of quadrate. The 

 coracoids are perhaps a little longer in proportion to their width, and the anterior notch 

 rather smaller than is the case with the ordinary forms. In the humeri the prominences 

 near the anterior angle of the distal end are vvelKdeveloped on both upper and lower 

 surfaces (see text-fig. 36, D, pr., pr.'). 



The dimensions (in centimetres) of some parts of this skeleton are : — 



Basioccipital : greatest width 9-2 



„ length 6-1 



width of occipital condyle 7"1 



height of occipital condyle 7"0 



Stapes : length 7-2 



Quadrate: extreme length 11-9 



width of necli .5'.5 



„ articular surface 48 



Articular bone : length 5-S 



Coracoid: length 23-3 



width lS-2 



Scapula : length 21-3 



width of blade o-O 



., distal expansion 14-4 



Humerus : length 15-6 



width of shaft at narrowest 6-9 



„ distal end 12-9 



k2 



