486 BRITISH FOSSIL REPTILES. 



' intermediate ' or ' antorbital vacuity,' in Pterosauria, has already been pointed out ; but 

 tlie comparable structure is by no means peculiar, as Von Meyer would lead one to infer, 

 to the skulls of Birds. ^ 



In no Pterosaurian has any obvious and unniistakeable suture been seen indicative of 

 the respective shares taken by maxillary (21) and premaxillary (22) in the formation of the 

 dentigerous part of the upper jaw^ : both hones combine to support the array of teeth ; they 

 have coalesced, at least at their external or faci-alveolar plates ; as, likewise, have the right 

 and left premaxillary portions forming the fore end of the upper jaw. The suture between 

 this preuiaxillo-maxiliary bone and the suborbital portion of the zygomatic arch remains. 

 Accordingly, there is a choice of analogies in the interpretation of the observed facts : a 

 proportion of the compound bone may be assigned to the premaxillary, according to the 

 analogy of the Crocodile and Lizard ; or the whole may be called premaxillary, according 

 to the analogy of the Ichthyosaur. 



GoLDFUSs, guided by the Lacertian analogy, limits the premaxillary to the anterior part 

 of the upper jaw, and to the upper part of the external bony nostril {n) ; and he illustrates 

 this view by a dotted line representing the assumed suture in his restoration of Ptero- 

 dactylm crassirostris, in pi. ix (op. cit.)." Von Meyer assumes, as arbitrarily, the Ichthyo- 

 saurian analogy, but views it as a specially Avian one, and ascribes to the Pterosauria a 

 bird-like premaxillary,'' and this determination is indicated by the numerals on the restora- 

 tion of the skull of Ptcrodactylus compressirosiris, p. 249, PI. 1, fig. 5. 



Of the maxillary bone (my 21) Von Meyer merely remarks that "it does not follow the 

 type of Birds" (" folgen nicht dem Typus der Vogel," ib., p. 15). And yet, if the Pterosau- 

 rian premaxillary be interpreted according to that type, forming so large a proportion of the 

 upper jaw as to include all the teeth, the edentulous maxillary must have had a correspond- 

 ingly Avian proportion and position. Only, whereas in most Birds the small and slender 

 maxillary sends up a process helping to define the back part of the nostril and fore part of 

 the antorbital vacuity, the corresponding process in Plerosaiiria would be (as indicated in 

 my PL 16, 22"), part of the premaxillary. 



I incline to believe, however, that it may prove to belong to the maxillary ; that 

 the dentigerous part of the upper jaw is due, in Pterosauria, to the combined maxil- 

 laries and premaxillaries, but that the latter take a larger share in the formation of 

 the alveolar tract than Goldfuss conjectures. One ground of such opinion is this : 

 the portion of upper jaw with six pairs of laniary teeth in the huge PlerodadyJus 

 Sedywickii, in which the palatal surface could be clearly worked out,* showed that the 

 anterior expansion, with the group of three pairs of teeth, could hardly have been 



' " Zwischen Nasenloeh und Augenbohle licgt eine driUe Oeffimiig, die wiederum an den Vogel- 

 si:badel erinnert." — Op. cit., p. 16. 



- Copied in PI. 1 {Pterosauria) of the present Work. 



8 " Ein Vogeln-ahnlichen Zwisclienkiefers," v, p. If), op. cit. 



"t Monograph, Suppl. No. 1 (1859), PI. I, fig.s. 1, a, b. 



