352 PEOF. ST. GEOEGE MIYAET ON THE 



The ilio-caudal process (Ic) is pointed and very long, extending directly postaxiad and 

 beyond the postaxial end of the ischium. The sacro-sciatic foramen is longer and more 

 pointed postaxially; at the anterior part of its dorsal margin a very distinct post- 

 trochanteric process (st) is developed postaxial to the antitrochanteric process, removed 

 from it by a distance rather less than the diameter of the acetabulum 1 . 



THE PUBIS 

 is more sharply bent down ventrad towards its distal end. 



THE ISCHIUM 



has its external smooth antero-posterior groove hardly, if at all, deeper than in Pelecanus. 

 The process (ps) in which it ends preaxially, is rather more marked than in Sula. 



The internal (ventral) groove (g) is much as in Pelecanus, but more expanded towards 

 its postaxial end. The part postaxial to the sciatic foramen is more expanded than in 

 Sula, and is more as in Pelecanus. 



The ventral surface of the ischium behind the sciatic foramen (and mediad of the 

 very strong ridge bounding medianly the antero-posterior ventral groove) is smooth ; it 

 is less concave than in Pelecanus, but more extensive than in Sula. 



THE RIBS. 



There are seven vertebral and five sternal. There may be eight vertebral ribs when 

 the eighteenth cervical vertebra bears one. 



THE VERTEBRAL RIBS. 



The first two have no sternal ribs ; all, or all but the last, have uncinate processes ; 

 these processes are more developed than in Sula. 



The last ends proximally in a filamentary process, and then ankyloses with the pelvis. 

 The first rib joining the sternum is the broadest. 

 None are much expanded distally. 



THE STERNAL RIBS. 



These increase in size postaxiad (Plate LXI. fig. 3). 



The last is not double generally, but may be so. 



The fourth is twice as long as the first ; the fifth is longer. 



None are very much expanded distally. 



The fourth and fifth may unite before joining the sternum. 



1 In 1182 c this process becomes an antero-posteriorly extended ridge. 



