IS88.] ANATOMY OF THE MESOSUCHIA. 437 



Pelvic Girdle. 



Ilium (Plate XIX. figs. 3, 4). — A flat, rudely rhombic bone, the 

 longer diameter of which is directed obliquely upwards and back- 

 wards. The acute antero-inferior angle is truncated by an oblong 

 surface (a.i), to which was attached the cartilage that connected it 

 with the anterior ischiatic process. The supero-anterior angle projects 

 forwards as a sharp spur (pa). The anterior border is stout, the pos- 

 terior thin. The upper border is rough and. narrow, it widens as 

 the spur is neared. The acetabulum (a) is wide and shallow, its 

 postero-inferior angle (p.i) is the stoutest part of the whole bone. 

 The median surface is strongly impressed by the sutural attachments 

 of the ends of the sacral ribs («, s). These impressions do not, as in 

 Metriorhynchus, rise to the level of the upper border, but they are 

 separated from this by a relatively wide, smooth surface comprising 

 an area of nearly g of the whole extent of this surface. 



Ischium (Plate XIX. fig. 5). — This resembles very closely that 

 of Metriorhynchus, from which it differs slightly by the rather 

 greater excess of its antero-posterior over its transverse dimension. 



Os Pubis (Plate XIX. fig. 6). — A paddle-like bone having a long, 

 slender, cylindroid shaft, and a flat dilated ventral extremity. The 

 anterior border is slightly concave, the posterior or inner border still 

 more so. The anterior, abdominal end is thin, and its outline curves 

 outwards and backwards. The pubi? is more slender in general form 

 than that of Metriorhynchus. 



Dimensions. 



Ilium (left). (No. 2 Leeds's Cat.) 



millim. 



Length, upper border 51 



,, including spine 78 



„ anterior border -)3 



„ posterior border 57 



„ inferior border 57 



Longer diameter 87 



Ischium. (No. 2 Leeds's Cat.) 



milliru. 



Length of median border 102 



Chord of anterior border , 70 



„ of external border 100 



Longer diameter of acetabular hollow .... 27 



Os Pubis. 



millim. 



Length Ill 



Breadth of ischiatic end "20 



Maximum thickness of ischiatic end 7"5 



Appropriate breadth of abdominal end .... 40 



Femur (right). — This presents the usual /-curve of the Crocodilian 



