April 19, 1888] 



NATURE 



599 



nostril. Behind the orbit is the temporal space, divided by a 

 bony bar into the supra- and infra-temporal fossae. 



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

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

 form the upper boundaries to the orbits, and are confluent pos- 

 teriorly with the parietals. 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 quadrate -jugal are of a some- 

 what unusual form ; the former bounding the lower half of the 

 orbit, and the latter inclosing 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 remarkable for its depth and extreme antero-posterior flatten- 

 ing ; and viewed from behind a pair of long rods are seen ex- 

 tending from its lower margin, one on each side, to the inner 

 angles of the quadrates. These bones are regarded as the 

 homologues of the basi-pterygoid 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, its 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. 



The back of the skull is essentially Lacertilian. A large par- 

 occipital bone extends outwards from the sides of the foramen 

 magnum, and its distal end, expanding, embraces the upper part 

 of the quadrate. The relation which the base of the parocci- 

 pital bears to the semicircular canals shows that it must be chiefly 

 formed by the opisthotic element, as Pi-of, 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, and about as thick as it is wide. The olfactory 

 lobe is small. Behind the cerebrum is a pair of large optic 

 lobes, occupying a prominent position on the sides of the brain, 

 and extending upwards well to the upper surface, but not meet- 

 ing above in the middle line. The region of the cerebellum 

 has been broken away, and its exact form therefore is some- 

 what uncertain ; but, judging from portions which remain, it is 

 tolerably clear that it extended between the optic lobes, and may 

 have reached as far forwards as the cerebrum. Attached to the 

 side of the medulla oblongata is a large flocculus, such as occurs 

 in this position in birds. 



It was the finding of the flocculus which led to the discovery 

 of some parts of the auditory apparatus. On clearing away the 

 stone in this region, a small tube filled with matrix was found 

 arching over the pedicle of the flocculus and dipping down be- 

 tween it and the optic lobe. This tube occupies the position of 

 the anterior vertical semicircular canal in the goose. By tracing 

 the canal backwards and downwards it was found to join 

 another similar tube forming an arch behind the flocculus — that 

 is, in just the position of a posterior vertical semicircular canal. 

 By careful excavation below the flocculus, a portion of a third 

 tube was found, arching outwards in a horizontal plane, and this 

 is believed to be the external semicircular canal. 



The similarity between the base of the fossil skull and that of 

 the Chameleon led to the inference that the fenestra ovalis would 

 be found to be similarly placed in both, and by clearing away 

 the niatrix from the orbit and temporal fossa this inference was 

 proved to be correct. The form and relations of the quadrate 

 bone make it highly probable that this Pterosaurian had no ear- 

 drum. 



A comparison of this fossil with the skulls of known 



Pterosauria leaves no doubt that it is more nearly related to 



the Scaphognathtis {Pterodactylus) crassirostris than to any other 



I species, but as it differs from that form, and is evidently new, it 



is to be named specifically Scaphognathus Purdoni. 



The Pterosaurian skull, as exemplified by this Lias fossil, 

 resembles more the Lacertilian than any other type of Reptile 

 skull ; and seeing that the skulls of birds and lizards are in many 



points very similar, one is not surprised to find in this fossil 

 characters which are also found in both these groups. In con- 

 sidering, therefjre, the relation which the Pterosaurian skull 

 bears to those of birds and lizards, the characters should be 

 especially noticed which serve to distinguish between the two 

 groups, thus : — 



1. In birds the brain-case is larger in proportion to the size 

 of the skull than it is in lizards. 



2. The quadrate, pterygoid, and palatine bones are movable 

 on the skull in birds, but more or less fixed in lizards.. 



3. In birds the hinder end of the palatine and front end of 

 the pterygoid are brought into close relation with the rostrum of 

 the sphenoid. This is not the case with lizards. 



4. The orbit is rarely completed by bone in birds, and never 

 by the jugal ; in lizards the orbit is surrounded by bone, and 

 the jugal forms part of it. 



5. In birds there is no prefrontal bone, while it is always 

 present in lizards, 



6. No bird has a supra-temporal bar of bone, but it is always 

 developed in lizards. 



7. In lizards the paroccipital process is large and formed by 

 the opisthotic ; in birds the paroccipital is small and formed by 

 the exoccipital. 



8. In birds the bones of the cranium are early anchylosed ; in 

 lizards they nearly always remain separate. 



9. Birds have the premaxillcc large and united into one bone ; 

 in lizards they are usually small. 



10. The ant-orbital fossa which is present in birds is only 

 occasionally present in lizard?. 



11. In birds there is always a lower temporal bar of bone ex- 

 tending from the maxilla to the quadrate. This bar is incomplete 

 in all lizards except Sphenodon, although well developed in other 

 reptiles. 



The skull of Scaphognathus Purdoni agrees with lizards in 

 the first seven of the above characters ; and with birds in those 

 numbered 8, 9, 10. Number 11 need not be considered, as it 

 can scarcely be regarded as distinctive. The greater importance 

 of the first seven characters makes it clear that in the structure 

 of the skull 5. Purdoni most nearly resembles the Lacertilia. 



The brain of Scaphognathus Purdoni agrees with that of 

 reptiles in its relatively small size ; while the separation of the 

 optic lobes by the cerebellum and the meeting of the latter with 

 the cerebrum, as well as the possession of a distinct flocculus-, 

 are important points in which it resembles the brain of the bird. 

 On the other hand, the form of the optic lobes is unlike that of 

 any living bird. 



The brain of the American fossil-bird, Hesperornis, shows a 

 striking resemblance to that of Scaphognathus Purdoni, for not 

 only is it proportionally smaller than in recent birds, but the 

 relation of the cerebellum and cerebrum to the optic lobes is very 

 similar. 



The facts above stated seem to show that the Pterosauria are 

 related to the birds in the form of the brain, and to the lizards 

 in the structure of the skull. This, however, does not constitute 

 the Pterosaurian a transitional form between birds and reptile-:, 

 in the sense of the Pterosauria having been derived from reptiles, 

 or of the birds having been derived from Pterosauria ; but lather 

 points to Aves, Pterosauria, and Replilia having been derived 

 from some common ancestral type. These relationships may be 

 thus indicated, taking only a few of the characters of each : — 



Lizard. 



Pterosaurian. 



Bird. 



Cerebellum small, op- Cerebellum large and Cerebellum large and 



tic lobes meeting, paroc- between optic lobes, par- between optic lobes, par- 



cipital formed chiefly by occipital formed chiefly occipital formed chiefly 



the opisthotic. by the opisthotic. by exoccipital. 



Ancestral Type. 



Cerebellum small, optic 

 lobes meeting, paroccipi- 

 tal small, and formed by 

 both exoccipital and opis- 

 thotic. 



Mathematical Society, April 12. — Sir J. Cockle, F.R. S. 

 President, in the chair. — The following communications were 



