136 MAEINE EEPTILES OE THE OXEOED CLAY. 



MycterOSUCllUS naSUtllS, Andrews. 

 [Plate VIII. ; test-figs. 51-54.] 

 1909. Steneosaurus nasutus, Andrews, Ann. Mag. Nat. Hist. [8] vol. iii. p. 302, pi. ix. fig. 1. 



Type Specimen. — A considerable part of a skeleton, including the skull (PI. VIII. 

 fig. 1), mandible (PI. VIII. fig. 2), atlas, axis, and nine other cervical vertebra?, two 

 or three crushed dorsals, forty-two caudals (PI. VIII. figs. 4-9), left coracoid and 

 scapula (text-fig. 54, C), left humerus (text-fig. 54 A, B) and ulna, left and part of 

 right femur, right tibia and fibula, astragalus, calcaneum, metatarsals, and other foot- 

 bones, also numerous scutes (PI. VIII. figs. 4, 10). The skull was figured in Ann. 

 Mag. Nat. Hist. [8] vol. iii. (1909) pi. ix. fig. 1. (R. 2617.) 



The skull (PI. VIII. fig. 1) in the type specimen has been much compressed verti- 

 cally and the snout is somewhat curved round to the right. In some respects it 

 approaches the Teleosaurus-type, particularly in the rapid preorbital narrowing of the 

 skull. The orbits seem to have looked more directly forwards than in Steneosaurus. 

 The frontals, prefrontals, outer face of the squamosals, and the parietals, all have their 

 surface sculptured by strongly-marked pits and rugosities, which occur even on the 

 summit of the high sagittal crest ; the surface of the snout is also sculptured, but here 

 the rugosities are less marked and. run, in the main, in a longitudinal direction. The 

 premaxillary expansion (pmtc.) was considerable and probably bore four teeth on each 

 side, of which the two hindmost are enlarged and set closely together; each of the 

 maxillae bears about thirty-eight teeth, which are nearly equal in size throughout the 

 series. The crowns of the teeth (PL VIII. fig. 3) are slender and sharply pointed ; 

 the enamel is marked by a series of very fine longitudinal ridges, one of which, on the 

 outer side, is rather more strongly marked and continuous than the others. 



The mandible (PI. VIII. fig. 2) is slender and has been much compressed vertically. 

 The upper surface of the symphysial region seems to have been somewhat convex from 

 side to side, while the ventral surface is marked by an ornamentation of irregular 

 longitudinal ridges ; there is a slight expansion at the anterior end, and the third and 

 fourth teeth are enlarged. The splenial (spl.) extends into the symphysis as far as the 

 level of the twenty-second tooth, and the hinder end of the symphysis is opposite the 

 thirty-seventh tooth. There are about forty-two teeth on each side. 



Speaking generally, the vertebroe are similar to those of Steneosaurus, but there are 

 some differences, especially in the caudal region (PI. VIII. figs. 4-9). 



The atlas and axis are not so long as might be expected from the great elongation 

 of the skull. The neural spine of the axis, instead of extending back nearly to the 

 level of the hinder ends of the posterior zygapophyses and rising gradually to its hinder 

 end as in Steneosaurus, is a low rounded crest, the highest point being near the 

 middle of its length, behind which it slopes downwards and disappears between the 



