190 ZOOTOMV. 



VIII. In the skull make out : 



33. The rounded brain-case, greatly encroached upon 

 in front by the large orbits or cavities for the eyes, and 

 continued in front into the slender tri-radiate beak. 



34. The foramen magnum (Fig. 47, f.m) a large 

 rounded aperture in the ventral wall of the hinder end of 

 the brain-case. 



35. The occipital condyle (o.c), a small hemispherical 

 elevation on the lower or anterior margin of the foramen 

 magnum. 



36. The lambdoidal ridge, a transverse ridge, a little 

 above and parallel to the upper border of the foramen mag- 

 num : it serves for the attachment of some of the muscles 

 of the neck. 



37. In the young bird the foramen magnum is bounded 

 by four distinct bones, one ventral, the basioccipital (b.o), 

 one dorsal, the supraoccipital (s.o), and a pair lateral, 

 the exoccipitals (<?.<?): the supraoccipital is bounded above 

 by the lambdoidal suture (l&.s), which separates it from 

 the parietals, and is represented in the adult by the lamb- 

 doidal ridge. 



38. A median longitudinal groove on the dorsal surface of 

 the skull, passing behind into a low ridge which unites with 

 the centre of the lambdoidal ridge : it marks the position of 

 the obliterated suture between the right and left parietals 

 and frontals, 



39. In the young bird the parietals (pa) and frontals 

 (fr) form two distinct pairs of bones, the former extending 

 a short distance forward from the lambdoidal suture, while 

 the frontals furnish all the anterior part of the roof of the 

 brain-case, and are continued forwards between the orbits, 

 to each of which the corresponding frontal furnishes a 

 supraorbital ledge. 



