LTASSIC FORMATIONS. 



63 



of similar size. Even in liJiampliorliijnclim Gemmingl the cranial convexity is not posterior, but 

 is limited to the temporal fossae behind the orbit, as in the specimen figured by Von Meyer 

 in pi. ix, op. cit. ; and this indication of the optic lobes is less conspicuous in the subject of 

 pi. X, fig. 1. In Dimorphodon there is still less trace of this alleged Avian characteristic. 



The bone which, in the Bird, as in the Pterosaur, forms part of the otocrane, articulates 

 with the cx- and par-occipitals behind, with the alisphcnoid in front, with the parietal above, 

 and with the petrosal within, which contributes the articular surface to the tympanic and 

 the upper rim to the meatus auditorius, also articulates in the Pterosaur, as in the Crocodile, 

 with the postfrontal : and this character appears to be constant in the Pterosauria as in the 

 Crocodilia, while it is exceptional in Aves. In the particulars in which the bone 8 differs 

 in the Pterosaurian from that in the Bird, it agrees with 8 in Crocodilia ; as e.^. in its high 

 position in the cranium, owing to the low development of the cranial chamber; its 

 greater degree of projection from the true cranial walls ; the extensive and suturally fixed 

 character of its articulation with the tympanic as compared with the more definite and 

 restricted glcnoidal movable articulation which the mastoid (8) affords to 28 in Birds. In 

 all these circumstances, whether the bone 8 (PI. XX, fig. 1) be called mastoid or squamosal, 

 it is Reptilian, not Avian, in the Pterosaur. 



Ilcrr Von Meyer states, in another of his comparisons, that in the MonUor, Iguana, and 

 Sfellio, tlie prefrontal (' Vorderstirnbein ') enters into the formation of the periphery of the 

 external nostril (Nasenloch).^ This is the case with Vamnus," not with true Monitors.^ 

 In Tcjus nigropunctatus some extent of the suture between the nasal and the maxillary 

 intervenes between the prefrontal and the nostril. The non-extension of the prefrontal to 

 the external nostril shows no Avian affinity in Pterosauria ; rather an agreement with the 

 majority of Beptilia, as, for example, with the whole order of Crocodilia. 



In some Crocodilia {Teleosaurus) and Laceriilia {Chlamgdosauriis, Lgriocephalus) 

 there is an antorbital vacuity, which, in the latter Lizard (PI. XX, fig. 3, a), is equal in size 

 with the nostril (ib., n) and intermediate in position between that cavity and the orbit (ib., o), 

 which is large. A process of the maxillary rises obliquely backward to join the nasal, and 

 to separate the intermediate vacuity from the external nostril. The lacrymal and pre- 

 frontal form the bar dividing the intermediate cavities from the orbit. In most Birds a 

 small intermediate vacuity is partitioned off from the nostril by a process of the maxillary 

 rising to join the nasal, and is similarly separated from the orbit by the lacrymal, which 

 descends to join the malar. The great range of variety in the development of this 

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



' 'Zur Fauna der Vorwelt,' fol., 1860, p. 16. 



2 See Cuvier, ' Ossemeiis fossiles,' v, pt. 2, pi. xvi, fig. 1 ('grand Monitor du Nil, Lacerta rii/ofica"), 

 p. 259, the Varamis Draccena of Menem, Varanus niloticus of most modern erpctologi>ts ; also in pi. xvi, 

 fig. 7, ' Monitor du Java,' p. 260 ; the Varanus hivittatus, of INIerrem. 



3 Ase.ff. Tupinambis teguixin, ' Sauve-garde d'Am^rique.' Cuvier, vol. cit., pi. xvi, figs. 10, 11, and 

 Thorictes Draccena, ib., tigs. 12, 13; 'La Dragone,' ib., p. 263. 



