8 FOSSIL REPTILTA OF THE 



The cranium has been slightly crushed and distorted by oblique pressure, due 

 to movements of the matrix after imbedding and petrifaction. The right halves 

 of the mid-frontal and nasal are depressed a little below the level of the left halves 

 of the same bones, and the right diverging branch of the parietal has been broken 

 from the rest of the bone, near the median line, and dislocated by the same pres- 

 sure from its union with the mastoid. The right ramus of the mandible, accom- 

 panying the movement of that side of the head, has been pushed so far below the 

 left ramus as to have its inner side brought into view in the profile of the skull 

 given in Tab. IV. 



The occipital conforms to the Lacertian type in the proportions and direction 

 of the par-occipital ; this process is long, narrow, straight, directed outwards, 

 compressed from before backward, and slightly expanded at the extremity, which 

 is applied to the back part of the mastoid and tympanic at the junction of those 

 boues. It has been slightly displaced, its end appearing on the left side at 4, 

 Tab. IV, with matrix intervening between it and the tympanic (28). A part of the 

 exoccipital which projects backward to contribute to the formation of the condyle, 

 is exposed near the mass of matrix, including the atlas vertebra and nuchal 

 dermal bones. 



The cranial part of the skull, posterior to the orbits, is shorter in proportion 

 than in the lizards, and resembles, in this respect, that of the crocodiles. The 

 parietal is short, and bifurcate behind, as in lizards. The body of the bone, or part 

 between the temporal fossae, is subcompressed where it forms the smooth, concave, 

 inner sides of those depressions, which do not meet above, but are separated by a 

 narrow, flat tract ; this might be converted into a ridge in older individuals. The 

 fore part of the parietal slightly expands where it is overlapped by the frontals. 

 Each hind branch of the parietal extends outward and a little backward ; its 

 pointed end is obliquely overlapped anteriorly by the inner branch of the mastoid, 

 completing therewith the hind boundary of the temporal fossa. The crushed and 

 dislocated state of the calvarium along its middle line does not permit the usual 

 evidence of a foramen parietale to be detected, but the appearances are against 

 such perforation being present. This foramen is not constant in modern lizards ; 

 the Scelidosaurus may agree with Cyclodus and Tejus in this respect. The parietal 

 bone, as a whole, plainly accords with the lacertian, not with the crocodilian, type 

 of that bone. 



The mastoid (8) is a triradiate bone, forming the upper and hinder angle of the 

 cranium, from which one ray passes inward to join the parietal (7), a second ray 

 forward to join the post-frontal (Tab. V, 12), and a third ray downward to join the 

 tympanic (28). A fracture of the body of the mastoid, by which the anterior branch 

 is broken away on the left side (Tab. IV, s), exposes a cancellous cavity, probably 

 forming part of the organ of hearing. 



