36 On the Structure of the Head in Ornithosaurs. 



EXPLANATION OF PLATES H. & IIL 



Plate II. 



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



thosaur. 

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

 Fiff. 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 tlie olfactory lobes. 

 Fiff. 4. The corresponding interior aspect of the frontal bone of Crocodilus 



Hastingi(B. 

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



marks the ca\'ity occupied by the fore part of the cerebrum — a 



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

 Fiff. 6. Restoration of the form of the cerebral cavity in the Ornithosau- 



rians from the Cambiidge Upper Greensand ; outline, seen from 



above. 

 Fiff, 7. Restored form of the cerebral cavity of an Ornithosaur, 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. 

 Fiff. 8. Restoration of the palate of the Ornithosaurian Ci/cnorhamj^/ms 



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



bone ; qa, quadi'ate articulation ; Pt, pterygoid ; P, palatine ; 



V, vomer ; Pm, premaxiUary ; Mx, maxillary ; m, malar. 



Plate HI. 



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



Fiff. 1. External appearance. 

 Fiff. 2. Interior appearance. 



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



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



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



invested with phosphate of lime. 

 Fiff. 3. Diagram side view of the Ornithocheiroid cranium, the shaded 



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



F, frontal; q, quadrate bone ; qj, quadi'ato-jugal; m, maxillary; 



PM, premaxiUary; d, dentary, a, articular end of lower jaw; 



N, nostril ; o, orbit. 

 Fiff. 4. Copy from Prof. Queustedt's figure of the head of Cycnorhamphus 



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



bones ; 23, postfrontal ; 26, quadrate ; G, quadrato-jugal ; 19, 



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



16, palatine. 

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



