No.2f.] SIIUFELDT ON NORTH AMERICAN TETRAONID^. 325 



yses. These apertures are found iu tlie vertebral canal in the remain- 

 der of the eervieals. Again, in both, the bodies are rather coicpressed 

 from side to side, and it is not until the bird has arrived at maturity that 

 the hypapophyses are well seen in these two segments. 



Now, taking up the eervieals from the fifth vertebra, we find certain 

 characteristics holding good throughout the series, with certain gradual 

 modifications. In the adult the neural spine in the fifth is prominent and 

 placed anteriorly ; it slowly subsides to the tenth, v/hereit is more tuber- 

 ous, nearer the middle of the bone, and bears evidence of having a 

 posterior projection overhanging the depression for the interspinous 

 ligament. This is thetj^pe to include the thirteenth, the projection being 

 more and more prominent and slightly cleft behind -, in the fourteenth 

 and fifteenth it suddenly assumes the broad quadrate spine of the dor- 

 sal type. Eeturniug to the fifth vertebra, we note another change in 

 the lengthening of the postzygapophyses ; the acme of this modification 

 is seen to be in the sixth and seventh vertebrtB. From these they gradu- 

 ally shorten again, while the anterior ones spread out with the dia- 

 pophyses to assume the form of the consolidated ones in mid-dorsal col- 

 umn. This arrangement allows lozenge-shaped apertures to exist be- 

 tween the segments above, and subelliptical ones laterally, that become 

 smaller and more circular above as the postzygapophyses shorten, and 

 quite large laterally as they approach the point opposite where the bra- 

 chial plexus is thrown off from the myelon. 



In the adult and old Cock of the Plains we detect beneath, in the 

 fifth vertebra, well anteriorly, a strongly developed quadrate hyijapophy- 

 sis. This process entirely disappears in the sixth, for in this segment the 

 centrum of the bone, anteriorly on either side, just where theparaop- 

 physes meet the body mesiad, a tubercle commences to make its appear- 

 ance, the apices slightly inclined towards each other. From the sixth to 

 the tenth inclusive these apophyses become longer, approach each other 

 below, but never meet so long as they have the " carotid canal," which 

 they form between them. In the eleventh they seem to have met tii rough- 

 out their extent to form a hypapophysis on the exact site they occupy 

 in the tenth, the tenth vertebra being the last cervical w^here there is 

 any evidence of the carotid canal ; hence from this method of formation 

 Professor Owen is made to say (Comp. Auat. and Phys. of Vertebrates, 

 vol. 11, p. 190), " In the Common Fowl each carotid * * * enters (iug) 

 the canal formed by the hypapophyses." 



In the completed twelfth vertebra of the mature bird we find tliis 

 hypapophysis very large, with expanded extremity, and the parapophy- 

 sis, on either side, sending down long subsquamous processes. In the 

 thirteenth segment of the "bird of the year" the parapophyses begin to 

 take on a change. This change develops in tbe adult still a perfect liypa- 

 pophysis, but in the younger individual the parai)ophysial element 

 begins to be notched anteriorly, a part favoring the pleurapophysis, a 

 part the centrum, so that in the fourteenth vertebra of the adult the 



