PEOF. H. G. SEELET ON DELPHIXOGNATHUS CONOCEPHALUS. 473 



ward. This is partly due to a remarkable sub-ovate notch, between 

 2 and 3 centim. wide and deep, which excavates the bone above it 

 in front. The upper border of the excavation is made by the malar 

 bone. I am not aware of a similar excavation in any other animal, 

 though the quadrate bone is similarly inclined forward in some 

 Omithosaurs and some Lacertilians. 



As the malar bone extends forward its contour ascends, so that 

 the hinder margin of the jaw forms a concave arch, the summit of 

 which, as preserved, is elevated above the inferior border of the orbit. 

 The state of preservation does not demonstrate the characters of 

 the anterior maxillary alveolar border, but the jaw was probably 

 straight and not concave in the dentary region as in the present 

 state of the specimen. 



The frontal bones appear to be paired at their anterior extremi- 

 ties. The nasal region is compressed, and prolonged the elevated 

 frontal area forward for some distance, before the jaw descended 

 towards its anterior extremity. 



The exact position of the anterior nares is not quite manifest^ 

 though they appear to be some distance in front of the orbits and close 

 together. The bones in the median line of the snout only show 

 that the jaw becomes much depressed in front. No teeth are seen 

 at its anterior extremity ; on the right side the alveolar border is 

 not preserved, and on the left side it is covered by the displaced 

 lower jaw. The maxillary teeth have mostly disappeared, and the 

 few which remain, imperfectly preserved, show a cylindrical type 

 not altogether unlike that of ProcolopJion, only the crowns are more 

 inflated. 



The lower jaw is short and remarkably deep behind the teeth. 

 Owing to the quadrato-squamosal articulation of the skull being 

 below the middle of the orbit, and the circumstance that the lower 

 jaw is not prolonged backward behind the condyle, it is much 

 shorter than the skull. Its coronoid region forms a sort of coronoid 

 process which exactly corresponds with and fits into the concavity 

 in the palatal contour in front of the orbit, formed by the malar 

 and squamosal bones. The hinder portion of this outline is long, 

 straight, oblique, and connects the rounded coronoid eminence with 

 the vertical articulation of the lower jaw. The inferior outline of 

 the lower jaw, convex behind, concave in the middle, is necessarily 

 developed downward as it extends backward ; so that, though the 

 total length of the mandible as preserved is only 20 centim., the 

 depth below and behind the coronoid is about 13 centimetres. 

 Hence the posterior half of the jaw has the aspect of being bent 

 downward at an angle of 45° with the dentary part, while its form is 

 obliquely oblong, and nearly twice as deep as is the dentary region. 

 The articular condylar surface is vertical, and so situate on the 

 infero-posterior extremity of the bone as to give the impression 

 that the larger part of the jaw is superior in position to the articu- 

 lation. The inferior border of the dentigerous region would about 

 pass through the middle of the condyle. It is therefore manifest 

 that, as the jaw extends forward, its vertical depth contracts, chiefly 



