South African Fossil Reptiles and Amphibia. 



169 



orbital bar and not as in Dicynodon. The downward processes of the 

 squamosals are also considerably expanded laterally. 



The occipital plate slopes backwards, so that the basal length of 

 the larger skull is 100 mm. The foramen magnum is fairly small, 

 the condyle tripartite and large. The lateral vacuities lie far apart 

 and at the level of the bottom of the foramen magnum. 



The lower jaw is short and the mentum is far back, the beak sloping 

 forwards gradually and fitting within the upper jaw. 



Associated with the larger skull is most of the postcranial 

 skeleton. 



FIG. 44. Prolystrosanrus natalensts, Htn. Type. No. 3715. x 



Of the vertebral column there are 34 vertebrae preserved 25 cervical 

 and dorsal, 6 sacral, and 3 caudal, The number of presacral and 

 sacral vertebrae is similar to that given by Watson for Lystrosaurus. 

 The total length of the column from the occipital condyle to the back 

 of the posterior sacral is 410 mm. 



The shoulder-girdle is almost entire. The sternum and interclavicle 

 cannot wholly be seen, the clavicles are slightly displaced, and the right 

 scapula has been crushed flat on to the ribs. The scapula is 85 mm. 

 long, 45 mm. broad at the upper end, 25 mm. broad at the acromion 

 process, and 35 mm. at the proximal end. The articular surface for 

 the precoracoid is 21 mm. long. Anteriorly it narrows to a point, but 

 posteriorly it is 17 mm. broad. The precoracoid is a rounded bone 

 25 mm. long and 27 mm. broad. It has a large notch on its upper 

 border. Posteriorly it forms apparently a small portion of the glenoid 



