Q. J. G. S. vol. xlviii.] 



[To face p. 82. 



POLACANTHUS FOXII. 



Fi-. 1. K 





r 



i ^ 



%A'^'^^i \ 



Explanation of Figures. 



1. Right iliuin and ischium, y^ natural size. 



To the right in the figure is seen the shield, with the dorsal ribs (r) passing under 

 the anterior blade of the ilium ; to the left are the 5 sacral ribs (.s) meeting the 

 acetabular region of the ilium. P = position of attachment for the pubis; 

 A = acetabulum ; Is = ischium. 



2. Left pubis : external aspect and posterior aspect, f natural size. 



The anterior blade of the bone is directed slightly outwards. 



/= surface for ilium ; A = articular surface for the pelvic acetabulum ; 

 Is = articular surface, presumably for the ischium ; pp — posterior process of 

 pubis, fractured ; m m\ on the internal visceral surface are two V-shaped 

 impressed articular surfaces, here indicated by dotted lines. 



