1901.] SHUFELDT — OSTEOLOGY OF THE CUCKOOS. 17 



Points of interest within the brain-case are seen in the presence 

 of a strongly marked longitudinal sinus and the unusual thickness 

 of the walls of the sella turcica ; its fossa, though deep, being quite 

 small, while at its base we find a double entrance for the carotids. 



As a whole the skull of Geococcyx is a delicate and a very light 

 structure for its size, air gaining thorough access to most of its 

 parts. 



The mandible (PI. I, Figs, i and 3), seen from superior aspect, 

 has the typical V-shaped form, with an extensive symphysis, which 

 is scooped out longitudinally above. Either ramus is not deep in 

 the vertical direction, while its upper and lower margins are promi- 

 nent and rounded, the former, however, becoming sharp as it 

 approaches the symphysis, which condition is sustained to the 

 mandibular apex. 



The ramal vacuity is large and occupies its most usual site; in 

 outline it is an elongated ellipse, but its anterior third is encroached 

 upon by a thin plate developed on the part of the dentary element. 



An articular end is considerably concave above and presents two 

 facets for the condyles of the quadrate ; its inturned process is 

 much tipped up, while the usual pneumatic foramen is seen near its 

 apex. Below, its convexity conforms with the convexity of the 

 articular excavation at its upper side, and its angle behind is 

 obliquely truncate from above downward in the forward direction. 



Beyond an articular end on the superior ramal border, we find, 

 on either side, the coronoid process but feebly developed and 

 single. 



When the osseous mandible is articulated in situ with the 

 remainder of the skull its tip does not extend quite so far forward 

 as does the apex of the superior osseous beak, a condition present 

 in the skulls of most Coracomorphtz and other groups. 



In the hyoidean apparatus we find fully the anterior two-thirds of 

 the glosso-hyal represented by a thin strip of cartilage, while behind, 

 where it ossifies in front, the usual median foramen is seen, having 

 an elliptical outline. Posterior to^this, on either side, the strongly 

 marked cerato-hyals project outward and backward. 



First and second basi-branchials do not anchylose with each 

 other, the former being short and thick, the latter about half as 

 long again and tipped off behind with cartilage. 



The elements of the thyro-hyals are long and slender ; they like- 



PBOC. AMER. PHILOS. SOC. XL. 165. B. PRINTED MAY 31 f 1901. 



