OF GALLINACEOUS BIRDS AND TINAMOUS. 205 
There is one more vertebra in the caudal region of Pterocles arenarius than in that 
of Syrrhaptes, and that which is the last cervical of the latter is the first dorsal of the 
former, because of the fact that in Pterocles it meets the sternum through the inter- 
vention of a hemapophysis; and this particular vertebra keeps distinct in Pterocles. 
The styliform ribs and the last, or sacral, have no appendage as in Syrrhaptes ; this 
last hemapophysis has a rudiment attached to it which really belongs to the arrested 
second sacral pleurapophysis. The same thing occurs in both genera. The strength 
of the vertebre of Pterocles agrees pretty well with that of the Pigeons, especially the 
cervical; the caudal are, however, feebler. The pneumaticity of the skeleton of Pte- 
rocles agrees with what we find in Syrrhaptes. There is no appreciable difference in 
the wing-bones ; but those of the leg are altogether stronger, and relatively of greater 
length as well. The great calcaneal sesamoid is also present. The middle metatarsal 
projects from between the other two, backwards, as in Syrrhaptes ; but the rudimentary 
hallux-bones have not been preserved in the specimen under description. Professor 
Owen (Osteol. Catal. Mus. Coll. Surg. vol. i. pp. 273, 274, Nos. 1421 & 1422) speaks 
of ‘‘ the long and slender tridactyle feet,” and also that ‘‘ there is no trace of a back 
toe.” Now assuredly there is a rudiment of this toe in Pterocles arenarius, P. setarius, 
and P. gutturalis, or else all the figures that I have at hand to refer to are wrong: it 
appears to be smallest in P. arenarius. The separation of the sacrum from the ossa in- 
nominata is kept up in Pterocles, as in Syrrhaptes ; but the filling-in of the sacral roof is 
more perfect, so that there is only a double row of small foramina, instead of the large 
fenestre that are seen in the pelvis of Syrrhaptes. For the rest, there is only additional 
strength to be remarked upon. 
The scapule are much more like those of the Grouse, and the tip of the bone is not 
nearly so premorse. There is no real difference between the furcula and the coracoids 
of the two genera of Sandgrouse; but the sternum is stronger, and the keel seems to 
project somewhat further at its apex. The episternum and hyosternal processes are 
exactly as in Syrrhaptes; but the external hyposternal processes are shorter, and the 
internal spurs are much more strongly bridged over to the xiphisternum. For the 
rest, the form of the hinder half of the sternum has the same pluvialine narrowness as 
in Syrrhaptes. 
On the Osteology of the Struthious congeners of the ‘‘Gallinacee.” Family ‘‘ Tinamine.” 
Example: Tinamus robustus. 
I approach this, by far the most arduous part of my task, with a feeling rather of 
intense caution than of actual diffidence. The linking-on of the great wingless birds 
with forms in which the organs of flight increase in relative size and actual perfection 
pari passu with a steady decrease in the bulk and dimensions of the individual creature 
has always been to me a matter of the greatest interest. Nevertheless my first im- 
