South African Fossil Reptiles and Amphibia. 61 



upwardly projecting beak and no pronounced mentuna descending 

 below the level of tbe bottom of the jaw. 



LYSTROSAURUS OVICEPS, sp. n. 



There is in the collection of the South African Museum the skull 

 and lower jaw (No. 641) of a small specimen of Lystrosaurus which 

 can be correlated with no hitherto-described species, and which is 

 therefore described here as a new species. It is said to have come 

 from the " Tarka Eiver, Cradock District," and is in a fine-grained 

 grey sandstone. 



The greatest length of the skull when viewed from above is 

 163 mm. The greatest breadth is 129 mm. The minimum 

 interorbital width is 46 mm. and the minimum intertemporal 

 width 25 mm. The orbit is elliptical with the long axis parallel 

 to the nasal plane ; its length is 36 mm., its height 33 mm. 



The snout is slightly convex with a median ridge, which is very 

 prominent in the middle of the premaxilla, but dies away at the 

 extremities of that bone. The premaxilla passes up as a narrow 

 prolongation between the nasals. Its greatest length is 76 mm., and 

 its width at the mouth measured round the bone is 56 mm. 



The maxilla is a rectangular bone, with a suborbital prolongation 

 supporting the jugal. The tusks are circular in section, and directed 

 slightly inwards. Their diameter at the base is 9 mm. ; length 

 probably 25 mm. The distance between the inner sides of their 

 bases is 46 mm. 



The septomaxillary forms a distinct part of the cheek, besides 

 being the posterior wall of the nostril. 



The fronto-parietal plane makes an angle of about 120 with the 

 general plane of the snout, but the change of slope is not very 

 abrupt owing to the convexity of the snout. The transverse ridge 

 across the nasals is not nearly so pronounced as in the other species. 

 The prefrontal forms the superior anterior quadrant of the orbital 

 border, but the supraorbital boss is very slight. 



The frontal forms the remainder of the upper border of the orbit, 

 and at the frontal junction is a slight median ridge. In each bone is 

 a slight but well-marked central boss from which lines of sculpture 

 radiate. These bosses are further from the median ridge than the 

 corresponding protuberances in L. declivis. 



The preparietal is large, circular, excavated, concave, and has a 

 maximum length of 19 mm. It forms the border of the anterior 

 third of the pineal foramen, which is of the keyhole shape common 



