AXIAL SKELETON OF THE PELECANIDJL 351 



Pelecanus, narrower (dorsoventrally) behind than in front, instead of the reverse, as 

 generally in Sula. 



The pubis is shorter and curved more sharply ventrad at its postaxial end. 



Viewed dorsaUy, the antero-posterior excess in length of the postacetabular part is 

 greater ; and the ilia expand at their preaxial ends in a wing-like manner, the external 

 margin of the ilium behind the expansion being much more concave, while a strong but 

 narrow ridge divides the two iliac fossa?. The sacro-sciatic foramina are about as visible as 

 in Sula ; but the postaxial margin of the pelvis is very different, the ilio-caudal spines (Ic) 

 projecting postaxiad generally more, often considerably more, than the ischium, and 

 nearly as much as the pubis. The angle formed by this spine with the adjacent margin 

 of the ischium is acute. The transverse diameter of the pelvis at the antitrochanteric 

 processes is even exceeded by that of the preaxial ends of the ilia. The postaxial half 

 of the external margin of the ischium is convex instead of being concave as it is in 

 Sula. The defects of pelvic ossification generally extend preaxiad to quite between 

 the acetabula (Plate LXI. fig. 2). 



Ventrally examined (Plate LXI. fig. 1), the pelvis of course repeats the characters 

 which can be seen thus as well as by the dorsal view ; and, in addition, the ventral surface 

 of the most preaxial part of each ilium extends more out laterally beyond the ends of 

 the transverse processes than even in Sula. There are generally three small presacral 

 foramina on each side the first the largest, the second the longest, the third the smallest 

 and round. 



The lateral acetabular fossae (f) are smaller than even in Sula, and rhomboidal in out- 

 line. The parapophysis of the second sacral vertebra, ankylosing, as it often if not gener- 

 ally does, with the ilium above, forms a complete postaxial boundary to the lateral fossa 

 in front of it that fossa extending above (dorsal to) the parapophysis of the first sacral 

 vertebra and at the same time to the posterior iliac fossa behind it. Thus there is no 

 trace whatever of the large opening which extends in Pelecanus above the expanded 

 ends of the sacral parapophyses. There is no supraacetabular fossa. 



The parapophyses of the last lumbar vertebra abut directly against the preaxial 

 margin of the acetabulum, instead of some distance preaxial to it as in Sula and 

 Pelecanus. The antero-posterior ridge inside the ischium, bounding its groove (g) 

 mesially, is more sharply marked than in Sula or Pelecanus ; and the extent of ischium 

 ventrad of the more postaxial part of that ridge is very much greater. 



THE ILIUM. 



This bone extends over the twenty-fifth (or last dorsal) vertebra and part of the one 

 preceding. 



Seen laterally, the dorsal margin of the preacetabular part is slightly more convex, 

 and its ventral margin is more convex preaxially and concave postaxially ; there is a 

 slight indication of an ilio-pectineal process (Ip). 



