the Head in Ornithosaurs. 27 



wide, margined above by a convex line most impressed be- 

 hind, and showing at intervals foramina like those seen on the 

 maxiUary bone of many of the lizards. In front is seemingly 

 the lower and back part of a perforation which, on the hypo- 

 thesis of the bone being maxillary, would be the left narial 

 vacuity, showing on its inner side an impressed ovate space. 

 On the upper part of the posterior lateral margin is an angular 

 notch, which may be merely due to fracture or may be the 

 anteorbital or middle hole of the skull. The least distance be- 

 tween these notches is about f inch. Internally (lig.2), between 

 the sides, the bone is convex and rapidly thickens from little 

 more than card-thickness at the palate to nearly f inch at a 

 height of 1^ inch from the palate. Externally at about this 

 height the bone rounds upward and inward for a quarter 

 of an inch, and then is truncated, with a small piece of rough 

 surface which looks obliquely outward and forward when the 

 external surface is vertical. On this surface and on a trun- 

 cated continuation upward of the narial boundary may have 

 rested the nasal bone. 



Putting the several known bones together, they appear to 

 indicate a cranium of such a form as is here drawn (PL III. 

 fig. 3), the light parts only being known, and the shaded parts 

 put in to complete the outline. Certain black lines running 

 through the shaded parts indicate possible boundaries of 

 bones. 



In completing the outlines I have rather followed the au- 

 thority of German specimens than my own ideas. For in- 

 stance, behind the orbit and between the frontal and squamosal 

 is a four-cornered space, representing the region in which the 

 postfrontal bone should be applied to the brain-case. The 

 diminutive representative of this bone is apparently seen in 

 many natatorial birds, such as the goose, between the frontal, 

 squamosal, and alisphenoid bones ; and in the immature stru- 

 thious skull Mr. Parker's researches have made its existence 

 evident. In birds the rudimentary bone has no other con- 

 nexion ; but in German Ornithosaurians it is usually of a tri- 

 angular form, and sends one limb to the quadrato-jugal bone. 

 And this is a point in which all birds differ from Ornitho- 

 saurians ; for, from the downward direction of the quadrate 

 bone in birds, the qviadrato-jugal and malar bones are removed 

 from all relation with the bones of the upper part of the 

 head. Yet seeing that in the Cambridge Omithosaur the 

 quadrate bone had an articular comiexion with the skull, it 

 is inconceivable that the quadrato-jugal should have had a 

 wide union with the postfrontal bone. But if the post- 

 frontal bone is obliterated, and the quadrato-jugal and malar 



