212 THE ANATOMY OF VEETEBRATED ANIMALS. 



the skull. From this point it sends a process forward to meet 

 the post-frontal, inward to unite with the parietal, and down- 

 ward to become connected with the pterygoid. A strong and 

 stout quadrate bone is connected wdth the exterior of the 

 skull, and presents a pulley-like surface to the articular piece 

 of the mandible. 



On the under-surface of the skull the long and slender 

 palatine bones are seen, bounding the posterior nares, which 

 are situated far forward. Behind, and separated by an inter- 

 val traversed by the rostrum of the basisphenoid bone, the 

 very large pterygoids commence, by slender and pointed ends, 

 w^hich lie on the inner side of the palatine bones at the level 

 of the posterior nares. They then widen, and passing back- 

 ward with a slight outward curvature, on each side of the 

 sphenoidal rostrum, end in three processes — one which con- 

 nects itself with the basisphenoid, another passes outward and 

 backward to the quadrate, while the third runs upward to the 

 squamosal bone. 



The lower jaw is composed of two rami, which unite, 

 anteriorly, in a very long symphysis. Each ramus is com- 

 posed of the normal six pieces, the splenial being remarkably 

 long, and entering extensivel}^ into the symphysis. 



We have no very clear knowledge of the structure of the 

 hyoidean apparatus in this reptile. 



The pectoral arch (Fig. 76, E) consists, upon each side, of 

 a narrow scapula ('S'c), having the direction usual in Lacer- 

 tilia^ and a broad coracoid (Co.), the inner edge of which does 

 not overlap its fellow, but meets it throughout in the middle 

 line, as in Plesiosaurus j so that, in this genus also, the rhom- 

 boiclal part of the sternum appears to have been absent or 

 /ery small. 



But there is a very distinct T-shaped interclavicle [I. Cl.), 

 the backward prolongation of which is received between the 

 anterior ends of the coracoids, while its horizontal bar is very 

 closely united with the inner ends of two stout curved clav- 

 icles ( CI.), the outer extremities of which abut against, and 

 are no less closely connected with, the upper part of the an- 

 terior edge of each scapula. This arrangement of the clav- 

 icles and interclavicle presents interesting conditions inter- 

 mediate between those observed in JVbthosatD^cs, on the one 

 hand, and those common in the Lacertllla, on the other. 



The scapula and coracoid give rise by their junction to a 

 glenoidal cavity, into which the tliick head of the very short 

 prismatic humerus (Fig. 70, B, TI) is received. The distal 



