LOWER LIAS. 11 



(Tab. IV) ; on the right side (Tab. V) it seems to be entire. The malar bone (26) 

 begins anteriorly, in a pointed form, between the lacrymal and maxillary, increases 

 in depth as it extends beneath the orbit, sends up a process which bifurcates to 

 receive the point of the post-frontal in the cleft (Tab. V, 27), and extends backward 

 and downward as a slightly convex and somewhat roughened plate, which articu- 

 lates by its lower convex, but somewhat irregular, border with the squamosal (27). 

 The posterior border of the malar presents a regular and well-defined, concave 

 curve. The chief peculiarity of the bone is its unusual vertical extent poste- 

 riorly. This extent seems to be increased by the squamosal (Tabs. IV and V, 27), 

 which articulates with the lower border of the produced part of the malar, and 

 expands to be articulated with the outer part of the lower half of the tympanic 

 (28), the upper angle rising above the terminal articular part of the malar. This 

 deep and powerful arch of bone, answering to the zygoma in mammals, may have 

 afforded attachment to large, masseteric muscles operating upon the lower jaw. 

 Similar muscles may have been extended between the ridges of the upper and 

 lower jaws. The tympanic is a long bone, compressed from before backward, 

 almost vertical in position, with a slight forward bend, but firmly wedged between 

 the mastoid and par-occipital above and between the squamosal and pterygoid below. 



The back part of the tympanic is convex transversely at its inner half, concave 

 at its outer half, where the margin is slightly produced to join the upper part 

 of the squamosal ; the inner part of the tympanic is more extended where it is 

 overlapped or abutted on by the pterygoid (Tab. VI, fig. 2, 24). Below this 

 expansion the tympanic becomes contracted and thickened, forming a kind of 

 neck to the terminal condyle. 



In the vertical position and length of the tympanic, Scelidosaurus resembles 

 the Lacertia ; in its fixity and extent of its connexions, it resembles the Cro- 

 coclilia. 



The lower jaw includes in each ramus an articular (29), a surangular (30), a 

 coronoid (30'), an angular (31), a splenial (32) and a dentary (33) piece. 



The articular (Tab. VI, fig. 2, 29) is situated in the inner side of the sur- 

 angular, and is thickened and projects inward to form the cavity for the major 

 part of the tympanic condyle, the outer border of which rests on the surangular. 

 This element (30) convex externally, presents a longitudinal ridge near its 

 upper part, which rises to join the posterior angle of the dentary element in 

 forming a low coronoid process. The angular (31) does not extend beyond the 

 surangular, but makes with it the angle of the lower jaw ; it grows in vertical 

 extent as it advances, is convex externally, unites with the dentary, and sends 

 forward from its lower part a pointed process between the dentary and splenial 

 elements. The splenial (32) makes a small appearance on the outer side of the 

 ramus, between the angular and dentary, but is chiefly visible as a broad, smooth 



