WEALDEN FORMATIONS. 



17 



In. Lin. 



Length of the scapula .... 



. 18 







Breadth of its base ..... 



. 8 







Breadth of its neck ..... 



. 3 



9 



Thickness of its base ..... 



. 1 







Thickness of its neck ..... 



. 2 



6 



Breadth of subacromial groove . 



. 2 







Breadth of humeral articulation 



. 4 







Breadth of coracoid articulation 



. 2 



6 



The coracoids (T. IV, 52) present a much more simple form than in the Megalosau- 

 rus, and resemble those of the Scink and Chameleon, thus deviating in their great 

 breadth, like the coracoids of the Enaliosaurs, from the Crocodilian type. In the 

 portion of the skeleton the right coracoid is slightly bent out of place and thrust under 

 the left one ; and there is no trace of a sternal or entosternal bone in their interspace. 

 The median margin of the coracoid describes an uninterrupted and full convex curve 

 commencing at the angle dividing it from the scapular articular surface ; but it is 

 separated by a concavity or emargination from the articular surface for the humerus. 

 It is perforated by a moderate-sized elliptical canal, about two inches from the 

 humeral articulation, and in this respect resembles the same bone in the Iguana, 

 Monitors, and Lizards, and differs from that in the Scinks and Chameleons. The 

 antero-posterior extent of the coracoid in the connected portion of the skeleton (T. IV) 

 is 8 inches ; its transverse diameter 5 inches. 



Tibia of the Hylaosaurus. T. VII. 



One of the long bones of a limb, with a phalangeal bone, and a scapula, of the 

 Hykeosaurus, were discovered in a quarry of Wealden stone at Bolney, in Sussex. 



The long-bone is figured by Dr. Mantell as a humerus.* It bears a much closer 

 resemblance to the tibia of the Megalosaurus,f but it is shorter and more expanded at 

 its distal end in proportion to its length. 



The proximal end (T. VII, fig. 3), which is 6^ inches by 3Jr inches in its long and 

 short diameters, shows a median tuberosity (a), divided by a depression from a second 

 smaller tuberosity ( b ) (this has been crushed in the specimen), which have articulated 

 with the condyles of the femur. Anterior and external to these the proximal end of 

 the bone is produced into a strong " procnemial " ridge ( c ), the front surface of which 

 is roughened for the insertion of a strong ligament. The shaft of the bone rapidly 

 contracts to a trihedral form, with the angles rounded off ; then as rapidly expands, 

 and becomes, as it were, flattened out ; more especially by the production of the outer 



Philosophical Transactions,' part ii, 1841. 



t Monograph, 1856, T. IX. 



