1888.] 



Scaphognathus Pnrdoni. 



437 



the bone separating the nasal aperture from the ant-orbital fossa is a 

 process of the maxilla. Alveoli for four teeth are preserved on 

 each side ; but it is not quite certain whether they all belong to the 

 pre maxillae. 



On the upper surface of the skull are to be seen the nasals and 

 prefrontals, on each side of the premaxillary process. The frontals 

 form the upper boundaries to the orbits and are confluent posteriorly 

 with the parietals. The supra-occipital region has been broken away. 

 Strong buttresses extend outward from the postfrontal and parietal 

 regions to form the supra-temporal bar. There is on each side a 

 large lachrymal bone forming the greater part of the upper and 

 hinder boundary of the ant-orbital fossa. The jugal and quadrato-jugal 

 are of a somewhat unusual form ; the former bounding the lower half 

 of the orbit, and the latter enclosing in an open V the greater part of 

 the infra-temporal fossa. The quadrate is a wide but thin plate seen 

 chiefly at the back of the skull. The base of the cranium is re- 

 markable for its depth and extreme antero-posterior flattening ; 

 and viewed from behind, a pair of long rods are seen extending from 

 its lower margin, one on each side, to the inner angles of the quad- 

 rates. These bones are regarded as the homologues of the basi-ptery- 

 goid processes of the sphenoid, such as are seen in some lizards and 

 birds, as for example in the Chameleon and Emu. 



From the point of junction of the quadrate and basi-pterygoid 

 process a bone runs along the palate, and dividing anteriorly forms 

 the hinder boundary of the internal nostril, it^ outer portion joining 

 the maxilla and its inner being continuous with a median bone 

 occupying the position of a vomer. This bony bar, it is thought, 

 represents the palatine and pterygoid bones, and its relations agree 

 better with those of the lizard than with those of the bird, seeino- 

 that it does not come into such close contact with the base of the 

 skull as it does in birds, but is thrust outwards by the long basi- 

 pterygoid process. 



The back of the skull is essentially lacertilian. A large parocci- 

 pital bone extends outwards from the sides of the foramen magnum, 

 and its distal end expanding, embraces the upper part of the quad- 

 rate. The relation which the base of the paroccipital bears to the 

 semicircular canals shows that it must be chiefly formed by the 

 opisthotic element, as Prof. W. K. Parker has shown to be the case 

 in lizards, and not by the exoccipital as it is in birds. 



By removing the frontal and parietal bones of the left side, a cast of 

 the brain cavity has been exposed, which there can be no doubt 

 represents the form of the brain, just as closely as does that of a 

 bird's cranial cavity. In proportion to the size of the entire 

 skull, the brain of this Pterodactyl is very small, being not more 

 than one-eighth of its length. Each cerebral lobe is oval in shape, 



VOL. XLJII. 2 1 



