ON BRITISH FOSSIL REPTILES. 149 



the alveolar borxler projects externally like a ridge, above -wliich the bone is 

 slightly concave. This ridge appears to be slightly dentated ; it overlaps 

 the corresponding alveolar border of the lower jaw. The posterior and su- 

 perior margin of the maxillary is slightly concave, and joins the malar and 

 lachrymal bones and a small part of the prefrontal : the anterior superior mar- 

 gin joins the upper half of the elongated intermaxillary, which divides it from 

 the nasal bones and the external nostril ; the lower side or base of the triangle, 

 M'hich forms the alveolar border, is convex. 



The most singular character of the cranium of the present fossil genus is 

 afforded by the intermaxillary bones. These, in their length and regular 

 downward curvature, give to the fore-part of the skull the physiognomy of 

 that of a parrot or accipitrine bird, but they differ essentially from both those 

 of the bird and lizard in being distinct from each other throughout their whole 

 length, and in gradually diminishing to their inferior extremity, which is not 

 expanded and continued laterally to form any part of the alveolar border of 

 the upper jaw. Each intermaxillary bone is a slender, subcompressed, elon- 

 gated bone, bent so as to describe a quarter of a circle ; the upper half is 

 thinner, but rather broader than the lower half, and is wedged in between 

 the superior maxillary, frontal and nasal bones ; the lower half, which is some- 

 what narrower but thicker, and is subcylindrical, projects freely doivnwards 

 beyond the superior maxillary bone; the deep anterior extremity or com- 

 pressed symphysis of the lower jaw is applied to the posterior surface of these 

 produced extremities of the two intermaxillaries, when the mouth is closed. 

 The two intermaxillaries converge towards each other from their posterior 

 origins, and are in close contact with each other, where they form the singular 

 curved projecting beak. 



The external nostril is single and situated between the upper diverging ends 

 of the intermaxillaries, but a fracture of the fossil at this part prevents the 

 precise form of this aperture, or the mode of termination of the nasal bones, 

 from being determined. The nasal bones, if not actually absent in the present 

 fossil, as in most Chelonians, must have been extremely small, as in the Cha- 

 meleons. 



The lower jaw is of considerable depth, and exceeds, as in most Saurians, 

 the length of the cranium. The articular cavity is deep and wide ; the angle 

 of the jaw is broken off directly behind this cavity on the left side, but is con- 

 tinued backwards beyond it for more than half an inch on the right side. The 

 ramus gradually expands in the vertical direction, and becomes thinner from 

 side to side, as it advances forwai'ds to about its middle part, which is just 

 behind the orbit, where it measures 11 lines in depth; it then begins gra- 

 dually to diminish vertically to the symphysis, which again slightly increases 

 vertically to its termination, which is obliquely truncated, much compressed 

 laterally, and applied against the deflected extremities of the produced inter- 

 maxillaries. The posterior half of the maxillary ramus is slightly convex ex- 

 ternally, the anterior narrower part is slightly concave ; the superior margin 

 describes a slight but graceful sigmoid curve, convex posteriorly, and con- 

 cave anteriorly, where it is applied to the convex alveolar border of the upper 

 maxillary bone, to the inner side of which it is closely adapted. The alve- 

 olar border forms an external, convex, projecting ridge, analogous to that of 

 the upper jaw. The composite structure of the lower jaw is very clearly dis- 

 played in the fossil. The articular piece is short, but is continued forward 

 as a slender process below the angular piece, as in the Varamis; the angular 

 piece is relatively larger than in the Varanus, and presents nearly the same 

 proportions as in the Thorictes. The supra-angular is larger, and occupies 

 the proportion of the jaw formed by the supra-angular and coronoid elements 



