I 



Type of the Genus Massospondjlus. 117 



preserved, is about 5^ inches, the articular head of the bone 

 is about 5 inches wide. The extremity is convex from within 

 outward, and forms two eminences on the superior surface, 

 one at the innermost angle and the other an inch further out- 

 ward, each being an inch wide, with an inch interspace 

 between them. The radial crest is not suddenly bent down, 

 as in Belodon, but curves outward and downward, so that the 

 superior surface is convex transversely and the inferior 

 surface concave towards the radial crest. The remarkable 

 lateral position of the radial crest, well defined from the head 

 above, is a distinctive character ; it extends vertically down 

 the shaft for 2^ inches, and is half an inch thick at its lower 

 extremity; it gives to the bone a width of less than 3 inches, 

 and an inch lower down, at the fracture, the width is about 

 1^ inch. This condition is closely approximated to by an 

 undescribed humerus in the Royal Museum at Stuttgart 

 referred to Zanclodon levis ; but there the radial crest is rela- 

 tively thinner, being ^ inch thick in a proximal fragment 

 which is 18i inches long, and the concave external outline 

 below the radial crest is less marked. The thickness of the 

 humerus of Massospondylus towards the middle of the shaft 

 is IjV inch. This end of the bone may also be compared 

 with the bone figured by Mr. J. W. Hulke as humerus of 

 Hylceosaurns *. 



The distal end of the bone is compressed from front to 

 back ; but there is no evidence to show wdiether the 

 proximal and distal ends were in the same plane, as would 

 seem probable. The distal fragment is a little over 3 inches 

 long at the fracture and nearly 2 inches wide ; it is S^^y inches 

 wide towards the distal articulation, which is transversely 

 extended, rounded, with the articulation extending about 

 \ inch on to the ventral aspect, and truncated on the internal 

 border. The shaft is compressed towards the external and 

 internal margins, and is broadly concave in the middle of its 

 length, so that two slight rounded ridges extend downward, 

 diverging towards the inner and outer angles of the articular 

 surface. On the superior side there is a moderate compression 

 on the external border. The compression of the distal end is 

 in harmony with that of the Stuttgart humerus already 

 referred to. 



There is no evidence of the scapular arch, of the ulna and 

 radius, or other bones of the anterior extremity. The rela- 

 tively large size of the humerus suggests ordinary quadru- 

 pedal movement. 



* Quart. Journ. Geol. Soc. 1874, vol. xxx. pi. xxxi. 



