Mr. D. M. S. Watson on the Cynodontia. 513 



Thrinaxodon liorhinus, Seeley, Phil. Trans. B, vol. 185, 



p. 990. 

 (" Galesaurus planiceps" in errore) ; Owen, Q. J. G. S. 



vol. xlili. pi. 

 (" Nythosanrus larvatus" in errore) ; Broom, Proc. Zool. Soc. 



1911, p. 900. 



Type-specimen, Brit. Mus. Nat. Hist. R. 511, a remarkably 

 complete skull and lower jaw with fragmentary axis and atlas 

 very well preserved and prepared. Locality " Orange Free 

 State," horizon unknown. 



R. 511a, an incomplete, well-preserved, adult skull, ob- 

 viously from the same locality as the type. 



ft. 3731, perfect skull and lower jaw, with fragments of 

 atlas, axis, and maims. Juvenile specimen, showing tooth- 

 change. " Griqualand." 



Broom's Ictidopsis, from the Lyslrosaurus-zone of Harris- 

 niith, where it is associated with Lydekkerina, may be 

 co-generic. It is not improbable that the type-skull may 

 have been found with the types of Lydekkerina. 



The skull and lower jaw of this species have been described 

 by Owen, Seeley, and Broom, and Woodward (under the 

 name Galesaurus) has given an interpretation of the palate. 

 The general structure in this family is well known. 



The more interesting new details are: — 



The occiput is triangular, the squamosal articulating with 

 the occiput low down, as in Cynognathus and Gomphognathus. 



The auditory groove is bounded internally by a shallow 

 long recurved process from the squamosal, very much in the 

 Gorgonopsid fashion, the groove not being carried out on to 

 the side of the head as in later Cynognathids. 



The quadrate complex is fixed into two notches in the 

 lower border of the squamosal. 



On the upper surface the relatively large size of the frontal 

 and lachrimal is noticeable. 



The nostril faces largely forward, and is not in any way 

 overhung by the anterior border of the nasal. The septo- 

 maxilla is small, has a small facial exposure, and is entirely 

 separated from the maxilla by the premaxilla below and the 

 nasal above. Between the septomaxilla and maxilla is a 

 small septo maxillary foramen opening on the side of the face. 



The brain-case is quite similar to that of Gomphognathus. 

 The foramen for the tenth nerve opens on the lower surface 

 of the triangular basicranial mass. The fenestra ovalis is a 

 small opening on the side of this mass. 



