62 Annals of the South African Museum. 



to species of Lystrosaurus and 8 rnm. in length. The boundaries of 

 the postfrontal are not seen, but it must have been a small bone. 



The parietal region is wide and flat. The parietals are small, the 

 postorbitals forming the whole of the upper borders of the temporal 

 fossae. These are transversely oblong in shape, 39 mm. broad and 

 25 mm. long. 



The squamosal has a pronounced ear-shaped expanded portion at 

 the outer border of the temporal opening, the projection being more 

 prominent than in L. latirostris. The zygomatic portion of the 

 squamosal is thin and flat. There is a large quadrato-jugal which 

 apparently forms part of the articular surface for the lower jaw. 



The development of the posterior part of the palatal surface shows 

 one or two interesting features. The pteiygoid is of the usual 

 Lystrosaurus type, having a long articulation w r ith the basisphenoid, 

 and an outward and backward process which extends to the stapes. 

 The basisphenoid is bent at right angles to the plane of the palate, 

 and is pierced by the two carotid foramina. 



Hitherto in Lystrosaurus the whole of the lateral bone extending 

 from the condyle to the squamosal has been called exoccipital ; but 

 this specimen shows that the so-called " exoccipital " is in reality 

 made up of two bones, the true exoccipital and the paroccipital 

 (opisthotic). The exoccipital is a small bone closely united to the 

 paroccipital, forming part of the condyle and of the wall of the 

 foramen magnum. The paroccipital is a large bone stretching from 

 the squamosal to the small exoccipital and having an inner down- 

 ward projection articulating with the basioccipital. It is pierced 

 near the exoccipital suture by the opening for the IXth-XIIth 

 nerves. 



The depth of the lower jaw at the symphysis is 34 mm. The 

 lowest point of the mentum is directly below the point of the tusk. 



This new species comes nearest to Lystrosaurus latirostris, from 

 which it differs, however, in the convexity of the snout, in the angle 

 between the fronto-parietal and premaxillary planes, in the ratio 

 between the interorbital and interternporal widths, in the shape of 

 the orbit, and in other minor features. When viewed posteriorly 

 the skull is seen to differ from both L. declwis and L. latirostris. 

 The parietal region is not grooved so deeply as in the type species, 

 and the zygomatic portion of the squamosal is much wider in 

 L. latirostris. 



