64 MR. C. W. ANDREWS ON THE SKULL AND 
ConcLupine REMARKS. 
In the preceding pages only a few of the types to which the fossils have been compared 
are mentioned, they being the only types to which any resemblances pointing to possible 
affinities could be made out. And even among these there are some to which the 
similarity is so slight that they also might perhaps have been omitted. For instance, 
in the case of Diomedea, it is only in the structure of the palate and one or two other 
points in the skull that any similarity with Phororhacos can be detected, the rest of 
the skeleton being strongly against any such relationship. In fact, it seems to the writer 
that the only groups that really come into question are the Falconiformes and aberrant 
Gruiformes, Cariama, Chunga, and to a less degree Psophia. 
It is toa relationship with the former group that the general appearance of the skull 
and feet of Phororhacos seems to point ; but, as above shown, the general structure of the 
skeleton, particularly of the pelvis and hind limb, is opposed to this, while, on the other 
hand, it is strongly in favour of affinity with the Gruiformes. In this, however, the 
skull at first sight seems to oppose a number of serious difficulties, differing widely 
from the skull of the typical Crane both in general appearance and in many points of 
structure, ¢.g. in its holorhinal nares and desmognathous palate; but it is precisely in 
these points that the Cariamide also differ from the typical members of the group and 
therefore resemble the fossil. Still the differences between the skull of Phororhacos and 
that of Cariama are so great that some explanation of them is necessary if the close 
affinity of the two forms is to be maintained. This explanation seems to be found in 
the extraordinary size of the beak in the fossil, a specialization that has led to great 
modifications in several regions of the skull. Thus the size and weight of the upper 
jaw have led to changes in the palate in the direction of greater rigidity, resulting in 
the extensive union in the middle line of the maxillo-palatine plates and their 
complete fusion with the anterior ends of the palatines (this occurs also in Toucans 
and Hornbills). Moreover, the development of the peculiar prominent ridges formed 
by these combined elements, and, as already described, projecting below the tomium on 
either side the middle line, also tends greatly to increase the rigidity of the beak, and 
possibly the modes of union of the pterygoids with the dasis cranii may still further 
add to it. 
Again, with the great massiveness of the mandible is correlated the large size of 
the temporal foss, and the weight of the skull as a whole has led to an increase 
in the area of the occipital surface by the extension of the lambdoidal and paroccipital 
crests, to which the muscles supporting the head are attached. ‘The characters thus 
accounted for give the skull of Phororhacos its peculiar form, so different from that 
of Cariama, and would be evidence of a high degree of specialization even if the 
rest of the skeleton were unknown. 
It was no doubt this high degree of specialization that brought about the extinction 
of this giant bird as soon as the conditions to which it was adapted underwent some 
