24 FOSSIL REPTILES OF DORSET. 



head ; they are six less in number than in Pies, dolichodeirus, 

 decreasing in dimensions forwards. The crowns of the large laniary 

 teeth of some are ten inches long, their transverse sections nearly 

 circular. The nares are placed anterior to the orbits and 

 near the highest part of the head. The femur is relatively 

 largely than in Pies. Hawkinsii, and exceeds the humerus by one 

 eighth of its own length. Besides some peculiarities in the skull 

 it shews an approach to the Crocodilian and Ichthyosaurian types 

 by the size of the head in relation to the body and in the 

 shorter but stronger neck. Number of carpal bones eight. From 

 the Ammonites planorbis zone, Lower Lias, Lyme Regis. 

 PLESIOSAURUS MACROMUS, Owen. 



While Pies, macrocephalns among other characteristics is distin- 

 guished by the superior size of the hind as compared to the fore- 

 paddle, in the present species the contrary proportions prevail, the 

 fore-paddle of the Pies, macromus is the largest, and in this respect 

 approaches the Ichthyosaurus. Below the head of the humerus 

 are two rough protuberances for the attachment of muscles; its 

 front part is slightly convex, the hinder part concave. The femur 

 differs in form as well as in size from the humerus, the front and 

 hinder margins being slightly concave. The skull and teeth of 

 this species have never as yet been found. From the Lower Lias 

 of Lyme Regis. 



PLESIOSAURUS OXONIENSIS, Phillips. 



Vertebrae remarkable for the almost circular outline of the 

 articular surfaces ; only a few of them have been found in the 

 Oxford Clay near Weymouth ; but they frequently occur in the 

 neighbourhood of Oxford, where a whole vertebral column has 

 been met with. The cervical vertebra shew a rapid augmentation 

 in size towards the head ; the caudal vertebrae indicate a rapid 

 contraction of the size of the tail, which must have been shorter 

 than is usual in this genus. The head was probably small ; the 

 whole length of the animal about fifteen feet. 



PLESIOSAURUS BRACHISTOSPONDYLUS, Hulke. 



This species is determined by Mr. Hulke from five middle 



