1901.] SHUFELDT — OSTEOLOGY OF THE CUCKOOS. 19 



has the epipleural processes fully as large as they are in the dorsal 

 series ; they are absent entirely, however, on the first pair of free 

 ribs. 



Returning to the atlas we find this segment rather delicately con- 

 structed, though in form it is quite like what we find in other 

 groups of birds, the Passeres for instance. Its neural arch is 

 narrow antero-posteriorly, though the canal is capacious. A perfo- 

 ration is seen at the base of the articular cup for the occipital con- 

 dyle, which cuts through the superior margin of this little concavity. 

 The centrum is small and does not develop anything that might be 

 called an hypapophysis. On the axis vertebra we note the presence 

 of a low, tuberous, neural spine, occupying the entire central por- 

 tion of the arch, while posteriorly on the under side of the centrum 

 a feebly pronounced hypapophysis is seen. The odontoid apophy- 

 sis is small and short as compared with other features of this verte- 

 bra, a fact no doubt due to the lack of depth in the atlas. At either 

 side of the centrum we observe a delicate and vertical spicula of 

 bone which completely arches over the vertebral vessels, constitut- 

 ing the last remnants of the lateral canal at this extremity of the 

 column. This condition is often met with among the Anatidce in 

 the axis vertebra of those birds. 



The postzygapophyses are directed backward and outward, and 

 are very powerfully developed, more so than in any of the first nine 

 or ten vertebrae of this portion of the column. The facets they 

 bear for articulation with the extremities of the prezygapophyses of 

 the third segment are at their under side about the middle. On the 

 third and fourth vertebras we also find a low neural spine placed at 

 the centre of either bone, while the hypapophysis is becoming 

 reduced in these segments, to disappear entirely in the fifth verte- 

 bra. These vertebrae, as in so many of the class, have their zygapo- 

 physial processes joined by a spanning lamina of bone, which in 

 either case and on either side is pierced near its middle by a small 

 elliptical foramen of the greater size in the fourth vertebra. 



The lateral canals occupy rathef more than the anterior halves 

 of the sides of the centra, and the processes that project from the 

 under aspects of their free margins behind are short, and each is 

 separated by a considerable interval from its fellow of the opposite 

 side. This great inferior width of the cervical vertebra is a char- 

 acteristic feature of these segments in Geococcyx, and is well sus- 

 tained throughout the series until we come to the free rib-bearing 



