from the Oxford Clay of PderhoroiKjh. .'iOl 



per cent, of the whole lengtli. In \\\& case of the mandible 

 the total length is 89 cm. ; that of the symphy.?ial region is 

 52 cm., or about 58 per cent. In the mandible figured by- 

 Bigot the total length is 100 cm., the lengtli of the sym- 

 physis is 66 cm. Both the proportions of the length of 

 preorbital portion of the rostrum to the whole length of the 

 skull and of the symphysis to the whole mandible are greater 

 than in other species. In S. megistorhynchus, which seems 

 to be the next most elongated form, tlio symphysial portion 

 of the mandible is only 50 per cent, of the whole. Another 

 characteristic of S. leedsi is the large number of teeth present, 

 there being 45—16 on each side of the upper jaw and 43-4-4 

 in the lower. 



In the skull the temporal fossse are very large and are 

 much longer than broad (length 12 cm., breadth 7*3 cm.). 

 The orbits are rather large and are oval in outline ; they look 

 upwards and outwards, as in other members of the genus. 

 The combined frontals terminate anteriorly in an acute angle, 

 considerably in front of the anterior border of the orbit ; 

 their upper surface is ornamented by a few scattered pits only. 

 The nasals extend back to about the anterior third of the orbit, 

 but their limit in front cannot be determined with certainty. 

 The anterior part of the snout was greatly flattened from 

 above downward : the end, formed by the premaxilla^, is 

 somewhat expanded. The facial processes of the premaxillse 

 are short and terminate in a blunt point opposite the interval 

 between the second and third maxillary teetli. On the palate 

 the maxillo-premaxillary suture is nearly straight and is at 

 right angles to the long axis of the skull. The palatal 

 surface is flat in the premaxillary regioii, but behind this it 

 is concave from side to side, the alveolar border forming a 

 somewhat sharply raised rim : the convex upper surface of 

 the symphysial region of the mandible fits closely into the 

 concavity of the palate. The upper teeth are 45-46 in 

 number. The two posterior premaxillary teeth are enlarged 

 and are separated by an interval nearly equal to the diameter 

 of their alveoli. The maxillary teeth are nearly equal in 

 size throughout the series ; they are directed downwards and 

 forwards. The individual teeth are slender and sharp; they 

 are slightly compressed at the extreme tip and the enamel is 

 marked by a series of fine longitudinal ridges. The sym- 

 physial portion of the mandible is slightly expanded anteriorly, 

 especially between the enlarged tliird and fourth teeth ; its 

 upper surface in this region is nearly flat, but behind it 



Ann. & Maq. N. Hist. Ser. 8. Vol. iii. 21 



