446 ME. ST. OEOEaE MIVAET ON THE 



Its proximal end is rounded, but more antero-posteriorly compressed than in the 

 second sternal rib. 



Its distal end is absolutely more but relatively less expanded ; and the two concave 

 articular surfaces are no longer subequal in size, but the ventral one (i) much exceeds 

 the dorsal one. 



The postaxial surface of the distal expansion of the bone exhibits large irregular 

 excavations. 



The postaxial surface of the shaft of this rib is flattened ; but its preaxial surface 

 exhibits a prominent ascending ridge. 



The Fourth Sternal Rib. 



The fourth sternal rib (fig. 76, iv & iv') is slightly more than twice the length of the 

 second, and is more curved, the concavity, of course, being also dorsal. 



The preaxial end presents a wider articular surface for the vertebral rib. 



Its distal end is only very slightly more expanded dorso-ventrally, and is therefore 

 relatively less so expanded. 



The disproportion between its two concave distal articular sui-faces is still greater, the 

 dorsal surface (s) being relatively still smaller. 



The postaxial surface of the distal expansion is still more excavated. 



The postaxial surface of the shaft is again flattened ; but the ridge on its preaxial 

 surface is much less marked. 



The Fifth Sternal Rib. 



The fifth sternal rib (fig. 76, v& v') is longer and slightly more curved than the fourth, 

 being about once and a half the length of the third sternal rib. 



Its proximal surface (for articulation with the seventh vertebral rib) is broader and 

 flatter than the corresponding surface of the fourth sternal rib, is absolutely rather less 

 dorso-ventrally expanded, and therefore very decidedly so relatively. 



Its articular surfaces (s & i) are still more unequal. Its shaft is more rounded post- 

 axially as well as preaxially, and there is no ascending ridge on either surface. 



The Sixth Sternal Rib. 



This rib (fig. 76, vi & vi') is longer again than the fifth one, but slightly less cui-ved ; its 

 length is decidedly more than two and a half times the length of the second sternal rib. 



Its proximal end is still flatter, and the antero-posterior dimension of its articular 

 surface is less inferior to its transverse extent. 



The sternal end of the rib is less extended dorso-ventrally than in any other sternal 

 rib, except the first, and its articular sui'faces have again approached each other. The 

 inner, or rather preaxial, margin of the shaft is sharper than in the other sternal ribs. 



