IN THE REPTILIA. 15 



being concave upwards. 'No bar extends posteriorly from the postorbital, which 

 joins the supratemporal, enclosing with it the infratemporal foramen. ISTo indication 

 of the supratemporal foramen can be found in the rather mutilated specimen. I think 

 it was not present. 



In Edafhosaueus Cope (Fig. 5, Plate II), the skull is of a more depressed type 

 than in the preceding genera. The postorbital is mainly preserved, and it is in con- 

 tact with the frontal (postfrontal) proximally, and sends out no bar posteriorly. There 

 was apparently no supratemporal foramen, but a very large infratemporal, which 

 extended well upwards. There is no parietoquadrate arch. An element, perhaps 

 supraoccipital, terminates in a free appressed apex on each side of the median pos- 

 terior region. This may be homologous with the small free bone described in 

 IsTaosaurus, in nearly the same position. The stapes is very large, and is at least 

 partially perforated near the expanded proximal extremity. It is probably fully per- 

 forated, as I have described it in the Diopeus leptocej^halus Cope. 



In Diopeus Cope, the supratemporal is elongate in the vertical direction, and as 

 elsewhere, it overlaps the quadrate at the distal extremity. Anteriorly, it sends 

 forwards a process probably for union with the postorbital bone, which is, however, 

 entirely free from the parietal, and encloses a foramen with it, precisely as in 

 Sphenodon. It further resembles the corresponding element in Sphenodon in send- 

 ing upwards a branch for union with the parietal. Thus there are in this genus two 

 posterior bars and two foramina, thus differing widely from the other Permian genera 

 of this or any other country known to me. Whether it has a free parietoquadrate 

 arch I do not know, but it is probable that the genus should be referred to the 

 Rhynchocephalia, in the neighborhood of Palaeohatteria Cred. It differs from 

 Sphenodon and resembles closely the Theriodonta in the absence of an obturator 

 foramen, and in the character of its dentition.* The zygomatic bone is not excavated 

 below, but has a straight outline to its junction with the jugal. The quadrate con- 

 dyle is double like that of Sphenodon and the Clepsydropidse (Fig. 8, Plate II). 



The Theriodonta described by Owen appear to have the single cranial arch 

 constructed in the same way as I described above as characteristic of the American 

 forms. I gather this from Owen's figures of the genera Kistecephalus Ow., Galesau- 

 rus Ow., Scaloposaurus Ow., Anthodon Ow., and apparently Lycosaurus Owen. 



The Anomodonta appear to have a differently constructed posterior cranial 

 region. In my study of the skull of Lystrosaurus Copef (Proceeds. Araer. Ass. 

 Adv. Sci., 1870, XIX, p. 205), I showed that this genus possesses an extensive supra- 



* Proceeds. Amer. Philos. Soc, 1884, p. 33. 



t Ptychognathus Oweu (preoccupied) ; Ptycliosiagou Lydekker, 1889. ■ 



