6 THE OSTEOLOGY OF THE REPTH^ES 



but doubtless when we discover the feet of the earliest reptiles we 

 shall find them not different from the feet of the contemporary am- 

 phibians. 



Every known bone in the skull of the Temnospondyli, except the 

 interfrontal of a very few, has been found in the skull of early rep- 

 tiles, and all, indeed, in a single genus Seymouria (Figs. 1,2) from the 

 Lower Permian of Texas. And there is no bone in the skeleton of 

 reptiles that is not known in these same amphibians, except the 

 preparietal of the Anomodontia, the supraorbitals of various Squa- 

 mata and the predentary and rostral bones of certain dinosaurs, and 

 doubtless the last two, if not all, are simply dermal bones which be- 

 came temporarily attached to the skull. The girdles and limbs of 

 the two classes are distinguishable only by minor characters. And 

 thus, while we do not know from these later rocks, and probably 

 never shall from rocks later than the Lower Carboniferous, all of the 

 characters common to the two classes in any one animal, from the 

 comparison of all it is not difficult to decide what were the primitive 

 characters of the reptilian skeleton in almost every detail. They 

 may be summarized as follows: 



The Primitive Skull of the Reptilia 



Rugose, with five openings in roof: 



A. Paired, divided, terminal nares. 



B. Paired orbits beyond middle [i.e., in front of the middle of the skull]. 



C. Median parietal (pineal) foramen. 



An emargination of the occipital border, between tabular and squamosal, 

 for the ear [the "otic notch"]. 



Seventeen pairs of roof bones; four pairs of palatal bones; eight pairs of 

 cranial bones; eight pairs of mandibular bones; three unpaired cranial 

 bones; one unpaired palatal bone — seventy-eight in all. 



A. Paired Bones 



1. Premaxillae (px) 1 p. . 



2. Maxillae (mx) / 



3. Septomaxillae (sx) Nasal bones 



4. Nasals (no) 



5 . Frontals (fr) 



6. Parietals (pa) 



7. Interparietals (ip) 



Median roof bones 



