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 hsemapophysis ; and this particular vertebra keeps distinct in Pterocles. 

 The styliform ribs and the last, or sacral, have no appendage as in Syrrhaptes ; this 

 last hsemapophysis 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 vertebrae 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 filUng-in of the sacral roof is 

 more perfect, so that there is only a double row of small foramina, instead of the large 

 fenestrse that are seen in the pelvis of Syrrhaptes. For the rest, there is only additional 

 strength to be remarked upon. 



The scapulae 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 " Gallinacea." Family " Tinamina." 



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- 



