14 THE OSTEOLOGY OF THE REPTILES 



Maxillae (mx). Primitively (Figs. 2 b, 3, 4, 6, 19, 21, 22, 33, 43), 

 articulating anteriorly with premaxillae, above with septomaxillae 

 and lacrimals, posteriorly with the jugals, ectopterygoids, and post- 

 orbitals internally, forming the outer boundary of both external 

 and internal nares in part. 



In most reptiles since Permian times they also articulate with the 

 nasals above {e. g., Figs, t,^, 43, 44) ; in the crocodiles (Fig. 69 b) with 

 each other on the palate, as also in many Anomodontia and Theri- 

 odontia. They are edentulous in the Chelonia (Figs. 30-32), later 

 Pterosauria (Fig. 72), some Anomodontia (Fig. 44 c), Dromosauria, 

 Ophidia, Saphaeosaurus, Ornithomimus, etc. The teeth may be in 

 single or numerous rows. 



Fig. 3. Pantylus (Cotylosauria), from side. Three fourths 

 natural size. 



Septomaxillae {sx). Small bones, the so-called turbinals of reptiles, 

 located partly within the nasal chamber, but appearing more or less 

 on the outer side at the back part of the external nares. (Figs. 33, 

 44 A, B, F, 45.) Present probably in all the earhest and most early 

 reptiles, and in most Squamata (Fig. 59); they are absent in the 

 Chelonia (Figs. 28-32) and Crocodilia (Figs. 68, 69). In some Dro- 

 masauria they extend back on the face to meet the lacrimals. Little 

 can be said about them in other extinct reptiles. 



Nasals (na). Articulating with premaxillae, frontals, prefrontals, 

 and lacrimals, forming more or less of the partition between the ex- 

 ternal nares. 



Except in most Cotylosauria (Figs. 2, 3, 22, 23, etc.), some Thero- 

 morpha and Therapsida, they also articulate with the maxillae on the 

 sides. They are absent in many Chelonia (Figs. 28-32) ; either absent 



