36 On the Structure of the Head in Ornithosaurs. 



EXPLANATION OF PLATES H. & HL 



Plate II. 



Fig, 1. Upper surface of the anterior part of the frontal bone of an Orni- 



thosaur. 

 Fig. 2. The same fragment, seen from the side. 

 Fig. 3. Interior aspect of the same specimen. 



In these figures o marks the upper boundary of the orbit, and 



ol the region occupied in the fragment by the olfactory lobes. 

 Fig, 4. The corresponding interior aspect of the frontal bone of Crocodiius 



Hastingice. 

 Fig. 5, Interior view of the frontal bones of a chicken. The shaded part 



marks the cavity occupied by the fore part of the cerebrum — a 



part which is not preserved in the fossil, fig. 3. 

 Fig. 6. Restoration of the foim of the cerebral cavity in the Ornithosau- 



rians fi'om the Cambridge Upper Greensand ; outline, seen from 



above. 

 Fig. 7. Restored form of the cerebral cavity of an Omithosaur, seen from 



the side. 



In these figures a marks olfactory lobes ; b, cerebrum ; c, optic 



lobes; d, cerebellum. A dotted line is introduced between c 



and a, which would give the cerebrum a form more like that of 



a bird, and which possibly may prove to be its true shape. 

 Fig. 8. Restoration of the palate of the Ornithosaui'ian Cyoiorhamphtis 



suevicus (Quenst.) : Bo, basioccipital ; s, sphenoid ; Q, quadrate 



bone ; qa, quadrate articulation ; Pt, pterygoid ; P, palatine ; 



F, vomer j JVn, premaxiUary ; Mx, maxillary ; m, malar. 



Plate IH. 



Portion of a bone supposed to be the maxillary bone of an Omithosaur. 



Fig. 1. External appearance. 

 Fig. 2, Interior appearance. 



m is towards the maxillary border ; na, a surface (perhaps 



articular) towards the nasal bone ; n, part of the boimdary of 



the nasal aperture. The inner surface of the bone is a good deal 



invested with phosphate of lime. 

 Fig. 3. Diagram side view of the Omithocheiroid cranium, the shaded 



parts being at present unknown : s, squamosal ; p, parietal ; 



F, frontal; Q, quadrate bone ; qj, quadrato-jugal; m, maxillary; 



PM, premaxiilary; d, dentary, A, articular end of lower jaw; 



N, nostril ; o, orbit. 

 Fig. 4. Copy from Prof. Quenstedt's figure of the head of Cycnorhamphus 



suevicus : 3, nasal bones ; 7, frontal ; 8, parietal and squamosal 



bones ; 2-3, postfrontal ; 26, quadrate ; 6, quadrato-jugal ; 19, 



malar ; 2, lachrymal bone ; 22, lachrymal bone ; 25, pterygoid ; 



IG^aiatine. 

 From this specimen is made the restoration PI. II. fig. 8. 



