22 MAEIISE EEPTILES OF THE OXFOED CLAT. 



of the bone as a curved ridge (orb.r.) aiinning towards the upper angle and forming a 

 rim to this part of the orbit. The upper angle is blunt and rounded, and bears on its 

 antero-internal face a surface (n.f.) for union with the nasal. A roughening {p\f.) 

 on the posterior edge probably marks the junction with the prefrontal, but this is not 

 clear in the specimens described. The anterior concave border (nar.b.) of the bone is 

 rounded and reflected inwards, forming the posterior border of the external nares. 

 On the inner face of the bone, at the lower end of the nasal border, is a rugose surface 

 (mx.f.) for union with the maxilla, to the outer face of which the lower part of the 

 lachrymal is closely applied. 



The nasals (text-iig. 12) are very large bones of peculiar form. They are prolonged 

 forwards to a great extent, their anterior portion being concealed beneath the pre- 

 maxillse, to the inner face of which they are here closely applied : they extend forwards 

 to a point about two-thirds of the total length of the rostrum in front of the anterior 

 border of the nostrils. Further back, by the divergence of the premaxillfe, they are 



Text-fiff. 12. 



anar.b mxj 



Eight nasal of OpJitJiahnosatirus from ouler side. (E. 2180, about g uat. size.) 



a.nar.b., anterior border of external nares ; lac.f., facet for laclirvmal ; mx.f., facet for maxilla ; 

 jjm.r./., facet for premaxilla ; p.nar.b., posterior portion of border of external nares. 



exposed on the surface of the snout, and extend backwards between the nasal openings 

 to behind tlie level of tlie front of the orbit. In this posterior region each is 

 divided by a rounded angle into two regions : (1) an upper, which with its fellow of 

 the opposite side forms the roof of the snout, which is somewhat concave between and 

 behind the narial openings ; (2) a lateral portion forming the upper border of the 

 nasal opeuuig, which is divided into an anterior portion where this upper border 

 [a.nar.l.) is thin and sharp, and a posterior region (p.nar.b.), separated by a process 

 projecting into the opening, where the edge is inflected to form a sort of funnel- 

 shaped channel. Immediately in front of the nasal opening the lower border 

 of the bone bears an elongated roughened facet for union with the corresponding 

 siu-face of the maxilla, which bounds the opening below. Just behind its narial border 

 the nasal has a roughened surface [lac.f.) for junction with the lachrymal, by which the 

 posterior border of the opening is formed. No specimen in which the posterior end of 

 the nasal is well preserved is known, but it seems to have been in contact with the 



