24 SHUFELDT — OSTEOLOGY OF THE CUCKOOS. [Jan. 4, 



This apophysis is very strongly developed in the last two vertebrae, 

 where it is also anchylosed to the centra, is bifid, and hooks well 

 forward to overlap the preceding centrum in either case. Each one 

 of these bones is pierced by pnuernatic foramina in a number of 

 places, as is also the terminal coccygeal vomer. 



This latter bone has an oblong irregular figure, with its posterior 

 margin considerably thickened, the others being cultrate. The 

 neural canal is continued into it for some little distance, its pas- 

 sage being denoted on the sides of the bone by a longitudinal smooth 

 elevation, which gradually tapers away to the postero-superior angle. 



Of the Sternum and Pectoral Arch. — The sternum of Geococcyx 

 is a thoroughly pnuernatic bone, but air does not gain access to any 

 of the shoulder-girdle elements. 



In the case of the former, foramina are chiefly found in the con- 

 cavities among the haemapophysial facets on the costal borders. A 

 few scattered ones may be seen in the median line upon the dorsal 

 surface. The number of these latter vary in different specimens. 



The " Road Runner " has a two-notched sternum, which gives 

 rise to a pair of flaring xiphoidal processes on either side. Its 

 carina is fairly well developed and moderately deep only. It ex- 

 tends the entire length of the bone, and is marked upon the upper 

 side of its projecting carinal angle by a roughened facet for articu- 

 lation with the hypocleidium of the furculum. 



Osseous welts are raised upon its sides to facilitate muscular 

 attachment, and these, in some specimens, extend on to the ventral 

 aspect of the body. The inferior border of the keel is somewhat 

 thickened. 



In front of the sternum a peg-like manubrium projects out, the 

 lower margin of which is longitudinally marked by a sharpened 

 crest. Below this, the perpendicular anterior border of the keel is 

 vertically concave, and this inferior manubrial crest is carried into 

 the excavation as a median raised line. 



Either costal border is very short, having but three facets upon 

 it, and these are usually close together. In front of them, on either 

 side, a prominent costal process is reared, constituting one of the 

 most striking features in this part of the skeleton of Geococcyx. 



The thoracic aspect of the sternum is very much concaved, the 

 ventral side being correspondingly convex. Here on this latter we 

 notice well-marked muscular lines, one on either side, commencing 



