Geological Society. 



577 



may be distinguished from the corresponding bones of known ex- 

 tinct gigantic saurians. One of these bones, believed to be a meta- 

 carpal or a metatarsal, is double the bulk of the largest analogous 

 bone of a full-grown elephant, though the metacarpals or metatar- 

 sals are much smaller in proportion in Saurians than in Pachyderms. 

 The bone is 7 inches in length, 9 in circumference in its middle, 5 

 in the antero-posterior diameter of its proximal end, and 4 inches 

 8 lines in the transverse diameter of the distal end. A proximal 

 phalanx is shown to be remarkable for its short and broad propor- 

 tions, which are more massive than those of the phalanges of exist* 

 ing Crocodilians or of the Poikilopleuron. 



An ungueal phalanx, also found at Chipping Norton, was 6 inches 

 in length, 2^ in breadth, and upwards of 3 in depth. It was slightly 

 curved, obliquely compressed, obtusely terminated with a shallow, 

 concave, trochlear articular surface, divided by a vertical convexity ; 

 it was marked on each side by a smooth curved groove, 3 inches 

 in length, with the concavity downwards, and the lower edge pro- 

 jecting beyond the upper at the posterior part of the groove ; but it 

 is shown to be by no means produced in so large and thick a ridge 

 as that which characterizes each side of the more depressed and 

 broader phalanx of the Iguanodon. From the ungueal phalanges of 

 that Saurian it differs in being much less compressed from side to 

 side and less curved downwards. It vastly surpasses in size any 

 of the ungueal phalanges of the Poikilopleuron. A smaller ungueal 

 phalanx, resembling in general shape the above, was found at Chip- 

 ping Norton ; and portions of metacarpal or metatarsal bones, agree- 

 ing in form and size with the fragments obtained at Chipping Nor- 

 ton, have been discovered at Buckingham : also a fragment 8 inches 

 long, which Prof. Owen considers to have belonged to a radius, a 

 fibula, or a long distal phalanx. 



With reference to a comparison of the remains of the Cetiosaurus 

 with those of the Polyptychodon, the bones of the extremities pre- 

 sent in both cases the cancellous structure throughout the central 

 part, which indicates aquatic rather than terrestrial habits. Prof. 

 Owen states that he has not found any of the remains of the extre- 

 mities of the Cetiosaurus to agree exactly in shape with those be- 

 longing to the Polyptychodon ; also that no specimen of a tooth 

 agreeing in characters with the teeth of the Polyptychodon has been 

 detected in secondary strata inferior to the greensand. Certain 

 large conical teeth, found in the Malton oolite, may, Mr. Owen 

 thinks, appertain to the Cetiosaurus, but he is of opinion that they 

 more probably belong to the Steneosaurus. 



In conclusion, it is stated that the vertebras described in the paper 

 prove the existence of a saurian genus distinct from the Mega- 

 losaurus, Steneosaurus, Poikilopleuron, Plesiosaurus, or any other 

 large extinct reptile, remains of which have been discovered in the 

 oolitic series ; that the vertebrae, as well as the bones of the extre- 

 mities, prove its marine habits ; and that the surpassing bulk and 

 strength of the Cetiosaurus were probably assigned to it with car- 

 nivorous habits, that it might keep in check the Crocodilians and 

 Plesiosauri. 



