1H90.] FROM THE WEALDEN AND PURBECK BEDS. 347 



The head is of triangular shape, much laterally compressed, and 

 measures about 0-lS in length by 0-16 in maximum depth at the 

 occiput. The cranial roof is broadest at the occipital border, gently 

 arched from side to side, and produced sufficiently downwards be- 

 hind the eye to form a considerable portion of the posterior border 

 of the orbital space ; there is a longitudinal median depression 

 attaining its maximum depth and greatest breadth immediately 

 behind the interorbital region and gradually becoming shallower in 

 front and behind ; while none of the bones appear to have been 

 ornamented, the only superficial markings being radiating rugae and 

 ridges, evidently due to the ordinary processes of growth. No details 

 of the cranial osteology can be deciphered ; but it is clear that there 

 was originally no ossified interorbital septum, and there is a frag- 

 ment of the 2Mras2)henoid (pas.) in position, which shows that this 

 bone was narrow in the middle region of the skull. In the mandi- 

 bular suspensorium, the hyomaiidibular (hm.) is conspicuous, but its 

 inferior portion and connections are unfortunately destroyed ; the 

 upper part of the bone is triangular in form, much expanded and 

 laterally compressed, and at the median constriction the direction of 

 compression becomes antero-posterior. Of the means of connection 

 between this element and the quadrate, nothing can be discerned ; 

 but the latter bone is well shown, in position, with its condyle 

 adjoining the socket of the articular element of the mandible. The 

 quadrate (qtt.) is triangular in shape, thinning out at its notched 

 superior border, — the hinder margin being thickened, gently arched, 

 turned outwards, and continued upwards as a long slender process ; 

 while the articular condyle is somewhat constricted from the main 

 part of the bone, and has a robust, inwardly-directed process arising 

 from its base. The last-named process is only distinguishable on the 

 left side of the fossil, but is there prominent and not readily 

 explained. Of the pterygo-palatine arcade, three elements are seen 

 from their outer lateral aspect. The metapterygoid (mpf.) is nearly 

 as deep as long, triangular, with a thickened superior border and 

 attenuated postero-lateral and antero-lateral margins ; it is gently 

 bent, being outwardly concave behind and outwardly convex in front. 

 The entopterygoid (enpt.) is broadest posteriorly, much elongated, 

 with a nearly straight outer inferior border and an irregularly curved 

 inner superior border, these gradually converging to a rounded apex 

 in front ; the bony lamina is placed more nearly in a horizontal than 

 in a vertical position, is sharply curved downwards at its postero- 

 lateral angle, and appears concave when viewed from the outer 

 aspect above. The ectopterygoid {ecpt.) is a long, narrow, lamelli- 

 form bone, apposed to the outer border of the entopterygoid, and 

 apparently extending somewhat in advance of this ; but its exact 

 form and proportions cannot be discerned. T\\& premaxilla (pmx.) was 

 evidently small, but only an imperfect fragment remains. The 

 maxilla (mx.) is a long, narrow, laterally compressed, and gently 

 arched bone, of almost uniform depth, except in its anterior third, 

 which gradually contracts and ends in a stout, inwardly directed 

 process ; the oral border is convex, and the hinder two-thirds of the 



