AXIAL SKELETON OF THE PELECANID^. 343 



The Ilium. 



This bone extends over the last and part of the penultimate dorsal vertebrae; and 

 ossification of fascia extends to the preaxial end of the last dorsal vertebra but two, i. e. 

 the twenty-second vertebra. 



Seen laterally, the preacetabular part is less convex dorsally, convex preaxially, and 

 concave postaxially at its ventral margin. 



There is a faint indication of an ilio-pectineal process, and a rudimentary posttro- 

 chanteric process (figs. 1 & 2, st). There are marked antitrochanteric processes [at). 



The postacetabular part of the ilium has its dorsal margin convex, sloping down 

 ventrad behind the last sacro-caudal, and giving out a short, postaxiad, slightly dorsad 

 process (the ilio-caudal process), which, however, may belong rather to the ischium. 

 This process is greatly extended, and becomes a long pointed process, in some species, 

 as before stated. It is never so wide and massive as in Pelecanus. The dorsal margin 

 of the sacro-sciatic foramen is more concave ; and the foramen is longer. 



The Pubis 

 is like that of Pelecanus, but extends even more postaxiad relatively, and its preaxial 

 part is less bent and convex ventrad. It is somewhat incurved mediad and very much so 

 distally. 



The Ischium 

 has its external smooth antero-posterior groove rather deeper and narrower than in 

 Pelecamis, but quite distinct ; the process (fig. 2, ps) in which its inferior boundaiy ends 

 preaxially is rather more prominent and distinct. The internal groove is longer, nar- 

 rower, and in a sigmoid curve (Plate LX. fig. -3, ff). 



The postaxial expanded part of the ischium is smaller ; and its postaxial margin 

 slopes more preaxiad and ventrad, and probably develops the ilio-caudal process pro- 

 jecting postaxially at about where it joins the ilium. 



The ventral surface of the ilio-ischium postaxiad to the sacro-sciatic foramen (mediad 

 of the ridge bounding the ventral ischiatic antero-posterior groove medianly) is a smooth 

 expanse, as also in Pelecanus ; but it is here less concave. 



TijE Ribs, 

 There are seven long vertebral ribs, and six or seven sternal ones. 



The Vertebkal Eibs. 



They increase slightly in length to the fifth or sixth, and expand generally somewhat 

 distally, especially the fourth, fifth, and sixth. The first four^ have long uncinate 

 processes, which arise more dorsad as we proceed postaxiad. They are a good deal 

 flattened and expanded towards the middle of their superuncinate part. 

 ' Pive sometimea — e. g. m 1186 b, c, and d, College of Surgeons. 



