SUPPLEMENT. 



249 



straight, largest in the anterior third, and smallest in the middle of the dentary 

 border. 



The shape of the dentary readily distinguishes this mandible from that of 



Pig. 78. Portheus sp. ; right maxilla, outer view, one half nat. size. — Zone of Holaster sxibglobosus ; Dover. 



B. M. no. P. 10813. 



P. gaultinus, and also seems to separate it specifically from the other known 

 mandibles of Portheus. It may perhaps prove to be the mandible of P. daviesi, 

 though the teeth are relatively high and narrow. 



Fig. 79. Portheus, sp. ; imperfect mandible, two thirds nat. size. — Zone of Holaster subglobosus ; Cherry Hinton, 

 Cambridgeshire. B. M. no. P. 10731. arj., articulo-angular ; d., dentary. 



Pachyrhizodus sp. (p. 132). Plate LIV, fig. 2. 



Part of a small head of Pachyrhizodus discovered by Mr. Henry C. Drake, 

 F.G-.S., in the zone of Holaster subglobosus at South Ferriby, Lincolnshire, is 

 interesting on account of the deepened shape of its premaxilla and the feebleness 

 of its'dentition. It displays the lower part of the left side, and is shown of the 



32 



