2S2 



OSTEOLOGY OF TUBINARES AND STEGANOPODES. 



bone in an Albatross, [ndeed, from the figures (21 and 22) I think one 

 would be rather led to believe that this sternum was a thick and heavy 

 one, so massive and ponderous appear all its anterior parts. But not 

 only these, but all its walls, wherever they will admit of it, are abso- 

 lutely honey combed with pneumatic cavities. All that bulging prom- 

 ontory in front of the bone is in exactly the same condition. 



The foramina leading to these cavities from without are very numer- 

 ous, and occur in groups in several localities. Chief among these is a 

 long, irregular, scattered row of them adown the entire median furrow 



of the visceral aspect of the sternal 

 body. Collections of others are found 

 up on the sides of the body on the 

 same surface ; some of these latter may 

 even perforate the bone. 



The principal entrances to the sides, 

 however, are through the collections of 

 apertures found at the bases of the in- 

 ter-articular fossae upon the costal bor- 

 ders. Sometimes these are so large 

 that we may obtain a view of the inside 

 and plainly see the osseous trabeculre 

 thrown across in various directions to 

 support the pectoral and visceral ster- 

 nal walls. 



Viewing this sternum from in front, 

 we notice a deep and broad median 

 notch, which is concave from side to 

 side, aud whose lateral walls on their 

 outer aspects are devoted to the upper 

 portions of the articular facets for the 

 coracoids. This notch is shut out of 

 sight from either a direct lateral view 

 or a view from above. Lower down 

 aud at the sides we hud the remainders 

 of the coracoidal facets. These nearly 

 meet behind the small manubrium; 

 then slope downward and outward. 

 They are concave in the vertical direc- 

 tion, but nearly straight the other way, 

 and they connect with the others spoken 

 of above at the upper sides of their in- 

 ner ends. 



Another facet is devoted to the coracoid upon the sternum of Diane- 

 dea. This is far removed from the first one, being concealed behind a 

 lip of bone at the outer aspect and at the base of either costal process. 

 This articular notch retains the end of the outer angle of the sternal 

 end of the coracoid in place when the arch is articulated as in life. 



Pig. 20. ITyoid arches of Diomrdea alba- 

 tnix. viewed from above; life size. From 

 the 8iiiii<- Bpecimen as Fig. 13. 



