162 Royal Society :— 
specimen then known was so incrusted with stalagmite that not 
much could be made of it. The present remains show that it was 
very markedly different in many respects from that of Didus. The 
cranium is narrower and longer, and without the peculiar frontal 
protuberance of Didus, being nearly flat at the top, with the fore 
and hind part elevated into two bony ridges of cancellous structure. 
The upper mandible also presents a remarkable difference from that 
of Didus, where the axes of the nasal process and the maxillary 
converge, whereas in Pezophaps they diverge. The maxilla also was 
relatively very small; and the mandible differed by being much 
straighter above, showing a salient angle on its lower edge (which is 
very inconsiderable in Didus), and being much more solid poste- 
riorly. In the quadrate the two birds are more alike. The rest of 
the bones of the head are wanting. 
A comparison of the entire skeleton shows that Pezophaps is in 
some degree, and perhaps on the whole, intermediate between Dedus 
and the normal Columbe, while it has some features, such as the 
armature of the wing, quite peculiar. It has no very near affinity to 
Didunculus ; indeed that form must be considered the type of a 
separate family, though not so aberrant as the Didide, which must 
be looked upon as the most remotely connected of the order Colum- 
bee. Strickland was amply justified in arriving at the conclusion 
that the Solitaire of Rodriguez was generically distinet from the 
Dodo; but it seems expedient to define his genus Pezophaps more 
precisely. Accordingly the following characters are assigned to it :— 
Rostrum mediocre, curvatum, processu nasali et ramis maxillaribus 
antice divergentibus. Frons plana, porca osseo-cancellata circum- 
data. Ossa coracoidea robusta. Ale breves, involatiles. Manus 
singulis bullis osseo-callosis armate. Collum et pedes longiores. 
In like manner the genus Didus may be defined :— 
Rostrum magnum, aduncum, processu nasali et ramis maxillaribus 
antice convergentibus. Frons tumida, in umbonem hypoconicum 
osseo-cancellatum surgens. Ossa coracoidea attenuata, scapulas 
obtuse attingentia. Alze breves, involatiles. Manus inermes. Col- 
lum et pedes breviores. 
The account given by Leguat of his Solitaire is then quoted in 
full, as also that of d’ Heguerty, the latter from Strickland, and the 
authors proceed to remark upon the different causes of extinction 
of species within historic time. This, when effected by man’s 
agency, is seldom done by man’s will; and various cases are cited 
to support this opinion. In extirpating species man generally acts 
indirectly ; and they succumb to forces set in motion indeed by him, 
but without a thought on his part of their effect. In the case of the 
extinction of the Solitaire of Rodriguez, the cause usually suggested 
seems inadequate ; and the authors consider it was probably effected 
by feral Swine, and quote a remarkable passage from an old French 
Voyage, showing the extraordinary abundance of these creatures in 
Mauritius, where, in or about the year 1708, above fifteen hundred 
had been slain in one day. It is plain that where these abounded 
