56 MR. C. W. ANDREWS ON THE SKULL AND 
odd bones referred to this species, but the following description is founded as far as 
possible on the associated set, which is the type-specimen. 
The Skull and Mandible. (Plates XIV. & XV.) 
The skull and mandible are in a wonderfully perfect state of preservation, and, now 
the matrix has been removed, all the important details of their structure can be made 
out. The skull has been slightly crushed, so that there is some dislocation of the 
bones of the roof, and also a slight compression of the beak, but otherwise it retains 
its original form. 
Occipital surface of skull of Phororhacos inflatus Ameghino, ? natural size. 
ir., lambdoidal ridge ; m.t., mammillary tuberosities ; oc.c., occipital condyle ; oc.t., occipital foramen ; 
p-p-, paroccipital processes ; sf.7., supraforaminal ridge; q., quadrate. 
The Occipital Region (text-figure, above).—The occipital surface is remarkable for its 
flatness, its great width from side to side, and the distinctness with which it is marked 
off from the other regions. This last peculiarity is due to the great development of 
the lambdoidal ridge (/.7.), particularly towards the sides. In its middle portion this 
ridge merely forms the angle (of about 100°) between the occipital and dorsal regions, 
but laterally it is produced outward, forming prominent lateral crests which are 
continuous ventrally with the broad paroccipital processes (p.p.). ‘These latter are 
convex posteriorly, both from above downward and from side to side; their inferior 
angles extend somewhat below the occipital condyle, and are formed by the ventral 
prolongations of the very well-marked supraforaminal ridges. ‘These ridges run 
downward and somewhat outward from the upper border of the foramen magnum (oc.f:), 
and form the inner borders of the paroccipital processes, separating them from a 
