NATURAL SCIENCES OF PHILADELPHIA. 185 



or.bital septum lias a large vacuity ; its thickened lower border 

 curves gently forward and upward. The vomer is slight and 

 readily detached. The optic foramina are merged in a large 

 vacuity ; the foramina in front of the ear are large and distinct. 

 The mastoid and postorbital are both prominent ; the depressions 

 for lodgment of the gland are well marked. The pterygoids are 

 remarkable for their breadth anteriorly, forming somewhat tri- 

 angular lammas, instead of irregular cylinders of bone. The 

 palatines are large, very broad posteriorly, and thin. The max- 

 illo-palatines, on the other hand, are very small and simple. The 

 very large and irregular lachrymals are permanently free from 

 surrounding bones, and seem to be usually (but not always) fenes- 

 trated with a large foramen. A prominent peculiarity of the 

 skull is the loose connection of the bones of both jaws. The 

 nasals are never entirely confluent with either maxillaries or pre- 

 maxillaries, and they are sometimes distinct throughout. The 

 posterior ends of the median prongs of the premaxillaries commonly 

 remain distinct from the nasals embracing them, and frequently 

 are not even anchylosed with each other. Traces of the rnaxillo- 

 premaxillary, maxillo-palatal,and maxillo-jugal sutures are usually 

 very plain ; and in the lower jaw, most of the original elements 

 remain more or less distinct throughout life. None of the cranial 

 bones appear to be pneumatic. 



An incomplete skeleton of Aptenodytes pennantii furnishes the 

 following additional osteological data (PI. 5; figs, all of nat 

 size) : 



All the bones of the wing are flat and solid. 



The humerus (Fig. 5), about 4^ inches long, has an average 

 width of an inch, and a thickness of about of an inch. IUs 

 perfectly laminar, except the globular expansion at its head. This 

 portion lies oblique to the general axis of the bone, the general 

 convexity of the articular surface presenting inward and back- 

 ward. The whole of this expanded surface is, in effect, the dome 

 roofing over an immense antrum, into which the whole end of 

 one's finger may be thrust. The articular surface is somewhat 

 crescentic in general outline ; anteriorly it slopes to the promi- 

 nence representing the "greater tuberosity," which is directly 

 continuous with the front edge of the bone. Inside this ridge 

 there is a deep groove, and along the inner border of the articular 

 surface lie two fossae separated by a ridge. But the distal extrem- 

 13 



