FOSSIL REPTILES OF DORSET. 29 



in their extreme shortness as compared with depth and breadth, 

 the length near the head being only one and a-half inch. The 

 most complete example of the head of a Pliosaurus which has as 

 yet been met with was found in the Kimmeridge Clays of 

 Kimmeridge, which I had the pleasure of presenting to the 

 British Museum, as well as the lower-jaw of the next species, PI. 

 troclianterius. It is five feet five inches long from the muzzle to 

 the proximal end of the jaw in a straight line and five feet eleven 

 inches if the outer curve is followed. There are about twenty- 

 seven or twenty-nine alveoli on each side of the upper-jaw and 

 twenty-five or twenty-six on the lower, of which five on each 

 side constitute the premaxillaries ; in some of the alveoli the 

 summits of the crowns of several successional teeth appear. The 

 bony palate is perfect except in the palato-nares region, and the 

 symphysis of the lower jaw is brought forward far beyond 

 that of PI. trochanterius, which extends back to about the twelfth 

 alveolar. 



PLIOSAURUS TROCHANTERIUS, Owen. 



This species is so named by Sir R. Owen on account of the 

 humerus and femur having a trochanterian ridge, which extends 

 some way down the shafts of each. In addition to this deviation it 

 is also conspicuous in the greater proportion of the teeth being 

 lodged in the symphysal part of the jaw. Some years ago I 

 recovered from the cliffs of Kimmeridge portions of the remains of 

 two individuals of this species, one an entire lower-jaw containing 

 fourteen sockets in each ranius, ten of which occupy the symphysal 

 part. It measures four feet two inches in length and two feet 

 two inches in breadth where it articulates with the skull. The 

 upper-jaw escaped my search, but I found the posterior part of the 

 cranium, shewing the condyle, which is two inches eight lines in 

 basal diameter, and the foramen magnum, which is one inch three 

 lines across. The occiput is traversed longitudinally by a high 

 ridge slightly expanding below. Presented by me to the British 

 Museum. 



