54 FOSSIL REPTILIA OF THE 



which Institution they were liberally presented by their discoverer H. B. Mackeson, 

 Esq. They were mutilated in the attempt to disencumber them of the massive blocks 

 of the matrix in which they were imbedded, and: are less characteristic than when 1 

 took the foregoing description and sketches of them on the spot where they were 

 found. 



" It has been shown that the texture of the femur, tibia, fibula, and the other long 

 bones, is conclusive against the identity of the Saurian of the Hythe Lower Green- 

 sand with the great ambulatory Dinosaurian reptiles, viz., Iguanodon and Megalosaurus, 

 the former discovered in the Lower Green-sand at Maidstone, and both species also in 

 the Wealden and Oolite Formations; there then remains to be considered its relation- 

 ship with the Enaliosaurians, the Crocodilians, the Mosasaur, and Poikilopleuron. 



The length, thickness, and indication of condyles in the femur, and the length, 

 thickness, and angular form of the metatarsals, place the Plesiosaurs, and, a fortiori, the 

 Ichthyosaurs, out of the pale of comparison. 



The superior expanse of the pubis, and the broad coracoid (?) with the form of the 

 femur, and the gigantic proportions of all the bones, forbid a reference of the Saurian 

 in question to any subgenera, recent or extinct, of the Crocodilian Reptiles, of which 

 the bones of the extremities were previously known. 



If it were true that the Mosasaurus had locomotive extremities in the form of 

 flattened paddles, like the Plesiosaurus, the identity of our present Reptile with the 

 Maastricht species would be at once disproved, by the unequivocal remains of the 

 metatarsal bones, which indicate a form of foot, corresponding, as far as the skeleton 

 is concerned, with that of the Crocodile : and if, as is most probable, the metatarsals 

 of the Lacertian type from the Green-sand of New Jersey appertain to a Mosasaurus, 

 the metatarsals from the Green-sand at Hythe differ from them in size, shape, and the 

 absence of any medullary cavity. 



With regard to the Crocodilians, the extinct genus which most closely agrees with 

 the characters of the bones of the Hythe Saurian is that which I have named Cetio- 

 saurus, the vertebrae of which have been found in the Wealden and Oolite formations, 

 and the long bones of which are devoid of a medullary cavity. Unfortunately no 

 vertebra referable to Cetiosaurus has yet been discovered in the Cretaceous deposits. 

 It is possible that the teeth on which the genus Polyptychodon has been founded may 

 belong to Cetiosaurus ; but hitherto such teeth have not been discovered in the strata 

 where the remains of Cetiosaurus are common. 



The gigantic Saurian discovered by M. Deslongchamps, in the Oolite at Caen, 

 and which he, has named Poikilopleuron Bucklandii, yields for comparison with the 

 Hythe Saurian the femur, fragments of the tibia, fibula, and metatarsal bones. 



In the form of the condyles of the femur, and their posterior intervening channel, 

 the Hythe Saurian resembles the Poikilopleuron more than it does the Iguanodon ; 

 but the large medullary cavity in the femur of the Poikilopleuron distinguishes it as 



