1901.] SHUFELDT — OSTEOLOGY OF THE CUCKOOS. 21 



where this canal is moderately well protected by lateral walls, but 

 in none of the series does it become a closed passage as in some 

 other birds. In the eleventh vertebra its place is taken by a strong, 

 single and median hypapophysis. 



This last becomes faintly tricornate in the twelfth vertebra, 

 markedly so in the next segment ; the three prongs springing from 

 a common pedicle in the fourteenth, which pedicle is lengthened 

 in the fifteenth ; still larger but without terminal prongs in the six- 

 teenth vertebra, to be entirely absent in the succeeding segment 

 and the rest of the column. 



In the atlas the neural canal is capacious and transversely elliptical. 

 From this vertebra it gradually changes its form and contracts in 

 calibre, until in the fifth vertebra we find it nearly cylindrical in 

 shape and much reduced in capacity. 



Passing down the series it gradually changes for a second time, 

 so that in the eleventh vertebra it is again found to be large and 

 transversely elliptical. This form it retains through the dorsal 

 series, though once more reduced in calibre. 



In the tail vertebras it is at first triangular with apex above, to 

 become a vertical slit as it enters the pygostyle. 



The fifteenth, sixteenth, seventeenth and eighteenth vertebrae of 

 the column in Geococcyx support ribs that meet to articulate with 

 costal ribs below. 



These ribs are broad above, but become more and more rod-like 

 as they near their haemapophysial articulations. The first three 

 pair of the series bear large epipleural processes, which are always 

 anchylosed to the rib upon which they appear. These three also 

 have costal ribs connecting them with the sternum ; this I believe 

 to be as small a number of the latter present in any living bird — 

 i.e., only three haemapophyses articulating with either costal border 

 of the sternum. The last pair of ribs, or those coming from the 

 eighteenth vertebrae, never have epipleural processes, and their 

 costal ribs do not reach the sternum. 



With respect to the four vertebrae that bear the ribs, we find 

 that they present all the characters of the dorsals as found among 

 Aves generally. The neural spines are lofty and quadrilateral in 

 outline, each having its superior rim capped off with a vertically 

 flattened tablet of bone. The diapophyses are rather broad, and 

 project directly outward from the sides of the vertebrae, having the 

 ribs articulating with them and the centra in the usual way. Very 



