416 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 20, 



Fibula, in. loths. 



Greatest length of its posterior or convex edge 4 5 



Length of the anterior or concave edge 2 7 



Diameter at half its length, from the depth of its anterior concavity 



to the posterior convex edge 3 7 



Tarsal bones. — Four in number; the three posterior bones being 

 large. 



Diameter of the largest of the three 2 3 



Ditto of the smallest 2 1 



The anterior tarsal bone is small, its diameter 6 



The metatarsal and digital phalanges consist of five ranges, larger 

 and broader than in the anterior paddles, but not being complete, 

 the number of digital phalanges cannot be enumerated. 



Proportions. — The whole length of the animal, as before stated, 

 is 16 feet 3 inches; for the sake of comparison I shall call it 1000. 

 We shall then have : — 



Length of lower jaw 160 



Length of neck » 24-5 



Width across lower jaw 78 



Length of humerus 67 



Width of distal extremity of humerus 35 



Antero-posterior length of coracoid 98 



Width of coracoid 47 



The length of the head is two-thirds the length of the neck ; it 

 bears the same proportion with regard to the thirty-four vertebrae 

 comprising the tail. 



P. megacephalus differs from the undernamed species in the fol- 

 lowing particulars : — 



P. Hawkinsii, Ow. P. megacephalus. 



The neck is three times the The neck is only one-third 



length of the head. longer than the head. 



The tail is two and a half The tail is but one-third longer 



lengths of the head. than the head. 



The cervical vertebrae are The cervical vertebrae are 



thirty-one in number. twenty-nine in number. 



The cervical vertebrae are The cervical vertebrae are 



smooth on their external surface, slightly rugose. 



The length of the largest of The whole length is sixteen 



four or five adult specimens does feet three inches, 

 not exceed seven feet six inches. 



P. dolichodeirus, Con. 



The neck is as four to one of The neck is as three to two of 



the head. the head. 



The head is as one to thirteen The head is as one to six of 



of the whole length of the ani- the whole length of the animal, 

 mal. 



