60 REPORT — 1841. 



Report on British Fossil Reptiles. By Richard Owen, Esq.^ 

 F.R.S., F.G.S., ^c. ^'c. 



Part II. 



The British Fossil Reptiles described in the first part of this Report pre- 

 sented modifications of their osseous structure, and especially of the vertebral 

 column and locomotive extremities, by -which they were especially adapted 

 for a marine life, and hence have been collectively termed Enaliosauria. 

 All the numerous species of this family are extinct, and it seems that the 

 genera have ceased to be represented since the deposition of the chalk for- 

 mations. In the present zoological systems the Plesiosauri and Ichthyosauri 

 are referrible to the Saurian order of reptiles, as defined by Cuvier ; but they 

 offer the most remarkable deviations from the existing types, and constitute 

 links which connect the Reptiles, on the one hand, with Fishes, and, on the other 

 hand, with the cetaceous Mammals. 



The present and concluding part of the Report on British Fossil Reptiles 

 contains an account of the remains of the Crocodilian, Dinosaurian, Lacer- 

 tian, Pterodactylian, Chelonian, Ophidian and Batrachian reptiles. 



The most remarkable of the extinct species of the amphibious and terres- 

 trial Sauria of England have been discovered and described by Dr. Buckland 

 and Dr. Mantell. Some remains are briefly noticed by Parkinson*, and by 

 the older English observers, as V/ooller and Chapman. Cuvier has added to 

 the value of these discoveries by his just observations and comparisons. Some 

 of the British Chelonian fossils have been noticed by Parkinson, Cuvier and 

 Dr. Mantell ; but none of the British extinct Ophidians or Batrachians appear 

 to have been hitherto recognized as such. 



Pliosaurus. 



The Enaliosaurs are immediately connected with the Crocodilian reptiles 

 by an extinct genus, represented by species of gigantic size, of which the 

 remains are not unfrequent in the Kimmeridge and Oxford clays. The Reptile 

 in question is essentially a modified Plesiosaurus, but its modifications appear 

 to entitle it to be regarded as a distinct genus, which, as it is more closely 

 allied to the true Sauria, I have proposed to call Pliosaurusf. 



Large, simple, conical teeth, with the enamelled crown traversed by well- 

 defined and abruptly terminated longitudinal or oblique ridges, as in the 

 teeth of the Plesiosaur, have not unfrequently been discovered in the Kim- 

 meridge clay formation. These teeth differ from those of the Plesiosaur in 

 their greater relative thickness as compared with their length, and in the 

 subtrihedral shape of their crown ; the outer side is slightly convex, sometimes 

 nearly flat ; it is separated from the two other sides by two sharp ridges ; these 

 are more convex, and the angle dividing them is often so rounded ofl^ that 

 they form a demi-cone, and the shape of the tooth thus approximates very 

 closely to that of the Mosasaur, with which it is equal in size. It may be 

 readily distinguished, however, even when the crown only is preserved, by 

 the ridges which traverse the inner or convex sides, the outer flattened surface 

 alone being smooth ; but an entire tooth of the present extinct Reptile presents 

 a long fang, which at once removes it from the acrodont group of lacertine 

 Saurians, and allies it with the thecodont Reptiles, among which it approaches 

 nearest, in the superficial markings of the crown, to the Plesiosaur. 



The known parts of the skeleton of the gigantic extinct reptile, to which the 

 teeth in question belong, confirm this approximation ; but the vertebrae of the 



* Organic Remains of a Former World, vol. Hi. 

 t Odontography, Part II., p, 282. 



