66 ODONTORNITHES. 



The first sternal rib of Hesperomis regalis, uniting above by the inter- 

 vention of the foiuth A r ertebral rib with the eighteenth, or first true dorsal 

 vertebra, is short and nearly straight (Plate IX, figure 16). It is 

 obliquely truncated in front, and has an articular face for union with the 

 sternum. The posterior end is expanded, somewhat rounded, and has on its 

 upper posterior angle an articular facet for the vertebral rib which joins it. 



The second sternal rib (Plate IX, figure 17) is longer and stouter than 

 the first, and somewhat more curved downward. Its articular faces are 

 similar, but the upper, or posterior, half of the shaft is much more 

 compressed. 



The third sternal rib is longer than the second, and somewhat less 

 curved (Plate IX, figure 18). Its distal end is more slender, and the 

 articular face oblique. The proximal, or posterior, portion is much flat- 

 tened transversely, and the lower margin of this end extends beyond the 

 articulation. 



The fourth sternal rib, which united with the seventh vertebral rib, is 

 long and slender, and considerably curved downward (Plate IX, figure 19). 

 Its anterior articular face is oblique, and the adjoining portion of the shaft 

 slender. The posterior extremity is expanded, and projects downward, 

 and backward, below the articular face. 



The next sternal rib, the fifth, did not unite directly with the sternum 

 in Hesperomis regalis, biit with the preceding rib near its base, and hence 

 its anterior extremity has no true articular face. It is long and slender, 

 curved downward throughout its middle portion, and its posterior end is 

 thin and expanded (Plate IX, figure 20). This rib united with the eighth 

 vertebral rib, and, in Hesperomis crassipes, it united also independently 

 with the sternum, by a well developed articular tubercle. 



The sixth sternal rib, in Hesperomis regalis, articulated with the 

 ninth vertebral rib, and, in front, was attached lightly to the sternal rib 

 last described. 



