1901.] REPTILES FROM PATAGONIA. 173 



septum, resembling that which in Chelys and Chdodina is formed 

 by a downward process of the prefrontal joining the palatine. 



Of the mandible (Plate XVII.) only the dentary-splenial 

 portion is preserved, with a fragment of the articulo-angular on 

 each side. The two rami are firmly fused at the symphysis 

 (fig. 1 «), which is gently rounded and not produced into a beak. 

 The oral margin is impressed with a broad, rounded groove, which 

 is bordered inside and outside by a rather acute edge. The limit 

 of the horny sheath is indicated by a distinct constriction (s.) on 

 each ramus, which extends across the dentary obliquely downwards 

 and forwards. 



Scapula. 



Except the scapula?, all remains of the appendicular skeleton are 

 too imperfect for description. The scapula of the right side 

 (Plate XVIII. fi!g. 1) is nearly complete distally, while that of the 

 left side is better preserved proxi^T)allJ^ The bone is rather stout 

 and laterally compressed, with a flattened outer face and an 

 expanded proximal end. The latter portion closely resembles the 

 proximal end of the scapula of M. platycepsm the British Museum. 

 The tuberosity {t.) is remarkably prominent, while the contracted 

 distal end is rounded. 



Carajjace. 



The remains of the shell are very fragmentary, and parts oaly 

 of the carapace can be recognized with certainty. The specimens 

 are insufficient to determine the original degree of convexity of the 

 armour, the pieces being not only too small but also probably a 

 little distorted in fossilization. The trunk, however, seems to have 

 been somewhat depressed. The bone of the carapace is thin, and 

 its irregular outer face shows that it was completely covered with 

 epidermal shields. The borders of the investing shields are marked 

 on the carapace either by deep rounded grooves, or by differences 

 in the elevation of the bone beneath adjoining shields. 



The largest fragment represents the left postero-lateral portion 

 of the carapace, and indicates that there were no fontanelles 

 between the costal and marginal bones. As preserved, its 

 convexity is very slight, while its outer face exhibits irregularities 

 which denote the borders of the last vertebral and costal and 

 three marginal shields. The edge of the row of mai'ginal bones is 

 excavated at intervals, so that the carapace is bordered by a series 

 of large triangular prominences. The sutures between the com- 

 ponent elements cannot be distinguished even on the inner face ; 

 but this aspect of the fossil is interesting as showing the expanded 

 upper end of the relatively small left ilium fused with a costal 

 bone. Miolania is thus proved to have been Pleurodiran in the 

 fi.xation of its pelvis. 



Caudal Sheath. 



The bony ring of a tail-sheath (Plate XVIII. fig. 2), originally 

 discovered by Mr. Santiago Eoth in 1897, is fractured at its 



