16 THE AMERICAN NATURALIST. 
shaped, and both dilated as well as truncated behind, where 
they do not reach the ilia by any means.  Pterocles has a very 
insignificant fourchette in its shoulder girdle, slender and of a 
U-pattern. Its clavicular ends articulate with the scapula. 
This they fail to do in all the pigeons I have examined, where 
the bone has much the same form and slenderness, but reaches 
a great deal farther down towards the carinal angle of the ster- 
num. As already stated above, both the sternum and the 
upper extremity of Pterocles are quite columbine in character, 
especially the former. Its sternum has considerably more 
pigeon than it has grouse in it, and as this bone is often seized 
upon by some avian classifiers as 7Ze index of a bird’s system- 
atic position and its affinities, it may account for the sand 
grouse having been placed upon the columbine side of the 
line in certain schemes of classification. 
With a strong columbo-tetraonine tincture in it, the pelvic 
limb of Pterocles arenarius has characters in it not commonly, 
if ever, found in those allied groups. In P. arenarius (No. 18,849, 
Coll. U. S. Nat. Mus.) the first metatarsal coóssifies with the 
tarso-metatarsus; is high up on the shaft; and the basal hal- 
lucial joint, with its unequal phalanx, is very rudimentary. 
There are but three joints and a claw in either outer podal 
digit; while the limb below the knee (there being no patella) 
is well supplied with sesamoids. One great grooved one is 
found back of the tibio-tarsal condyles, and two or three small 
ones in the sole of the curious foot of this bird. Air does not 
gain access into the shafts of the long bones of the pelvic limb 
of Pterocles; and this also holds true for Syrrhaptes (Parker). 
As to the systematic position of the sand grouse, it may be 
briefly said that there is altogether too much grouse in the 
skull of Pterocles to admit of its being arrayed with the 
Columba; while, on the other hand, there is too much pigeon 
in both Pterocles and Syrrhaptes to admit of placing either of 
these genera in the tetraonine assemblage. The place they 
really hold is an intermediate one, and this is best shown, I 
think, and the ends of classification best served, by arraying 
them in a separate group, — the suborder Pterocles, standing 
between the Galli and the Columba. 
