.Vo. 2.1 SnUFELDT ON NORTH AMEEICAN TETEAONID^E. 325 



yses. These apertures are fouud iu the vertebral eaual in the remain- 

 der of the cervieals. Again, in both, the bodies are rather compressed 

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

 the hypapophyses are well seen in these two segments. 



Xow, taking- up the cervieals from the fifth vertebra, we find certain 

 characteristics hokling good throughout the series, with certain gradual 

 modiiications. In the a(hilt the neural s]>ine iu the fiftli is promuient and 

 placed anteriorly ; it slowly subsides to the tenth, where it is more tuber- 

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

 posterior projection overhanging the depression for the interspiuous 

 ligament. This is the type to include the thirteenth, the projection being 

 more and more prominent and slightly cleft behind ; in the fourteenth 

 and lifteenth it suddenly assumes the broad fxuadi\ite si)ine of the dor- 

 sal type. Eeturning to the fifth vertebra, we note another change iu 

 the lengthening of the i)ostzygapophyses ; the acme of this modification 

 is seen to be in the sixth and seventh vertebrae. 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 i^ostzygapophyses shorten, and 

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

 chial plexus is thrown oft' 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 hypai^ophy- 

 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 ai>pear- 

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

 the tenth inclusive these apo[)hyses 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 tiirough- 

 out their extent to form a hypapophysis on the exact site thv y occui>y 

 in the tenth, the tenth vertebra being the last cervical where tliere is 

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

 Professor Owen is made to say (Comj). Anat. and Phys. of Vertebrates, 

 vol. 11, fi. 100), '" In the Common Fowl each carotid * * * enters (iug) 

 the caufil formed l)y the hypapophyses.'' 



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

 hypapophysis very large, with expanded extremity, and the i)arapopliy- 

 sis, on either side, sending down h>ug subsquamous processes. In the 

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

 take on a change. This change develops in the adult still a perfect hy [»a- 

 pophysis, but in the younger individual the parapo]»h\sial element 

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

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



