388 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [June 23, 



upper surface falls gradually from the proximal end, rises slightly- 

 over the shaft, and then again gently declines along the upper inter- 

 condyloid groove. 



Remarks. — The general configuration of this bone (particularly 

 the form of its extremities, and especially that of its proximal one) 

 proves it to be reptilian, and at the same time separates it from the 

 Enaliosauria, the remains of which are so common in the Kimme- 

 ridge clay of the Dorset coast. 



A comparison of it vdth several humeri and femora of recent 

 crocodiles and lizards leaves no doubt in my mind that it is the left 

 humerus of a crocodilian ; but its axis is less twisted and its proximal 

 end has a smaller upward curve than the humerus of now living 

 crocodiles, from which it also differs in its enormous size. This last 

 character also removes it from the extinct Crocodilia, the Teleosaurs 

 and Stenosaurs, from Goniopholis and Poikilopleuron, none of 

 which, so far as they are yet known to us, had humeri approaching 

 the magnitude of this bone. There are three genera to the indivi- 

 duals of which a stature correlative with the size of this Kimmeridge 

 humerus has been assigned — Streptospondylus, Cetiosarus, and Poly- 

 ptychodon. Not anything, so far as I can learn, seems to be known 

 of the limb-bones of Streptospondylus major, Owen; but those of 

 Polyptychodon and Cetiosaurus are described as having a coarse spongy 

 texture, and as being destitute of a medullary cavity. 



The evidence on which these statements rest, so far as it has been 

 accessible to me, does not appear to my mind to be decisive regarding 

 these two points. The portions of long bones referred by the late 

 Dr. Mantell to Cetiosaurus, formerly in his cabinet, and now in the 

 British Museum, are so fragmentary that, in the absence of any 

 record of their discovery in immediate association with vertebrae of 

 the recognized Cetiosaurian type to authenticate them, the correct- 

 ness of their reference to this genus is open to doubt ; and there is 

 the same uncertainty respecting the large bone in the Oxford Museum 

 provisionally assigned to Cetiosaurus, and also with regard to the great 

 Hythe saurian assigned by Prof. Owen to Polyptychodon. 



It must be conceded that the limb-bones of these two genera have 

 not yet been certainly identified ; and therefore statements regarding 

 their structure can be of little value. 



So far as relates to the absence of a medullary cavity, this Kim- 

 meridge humerus agrees with what has been published of Polypty- 

 chodon and Cetiosaurus ; but it completely difiers from them both in 

 the compactness of its tissues. 



It is also unKke the humeri of the Dinosaurs, Iguanodon and 

 Hylceosaurus ; and, so far as the material within my reach has enabled 

 me to judge, it is not like that of Megalosaurus ; but the bones in the 

 British Museum considered to be humeri of this saurian are too 

 fragmentary for the comparison with them to be final. 



The bone with which in its general features it agrees more closely 

 than with any other known to me, is one formerly in the late Dr. 

 ManteU's collection and now in the British Museum. It was re- 

 garded by Dr. ManteU as a right humerus (an opinion adopted by 



