2 ALLEN'S naturalist's LIBRARY. 



nasals* and the sternum with Hvo notches on each side of the 

 posterior margin, the inner one being sometimes reduced to a 

 foramen (Fig. 4). 



The bill resembles that of the True Game-Birds, but is not 

 so strongly developed. 



Three toes only occur, the hind-toe, when present, being in a 

 rudimentary condition. The feet are very short and feathered, 

 and the toes are either naked or thickly covered with plumes. 



The wings are long and pointed. 



The feathers of the body have well-developed after-shafts, 



Fig. 3.— Skull of/', alchatns. 



like those of the True Game-Birds, but the fifth secondary 

 flight-feather is absent. 



The young are born covered with down, and are able to run 

 soon after they are hatched. 



The eggs are almost invariably three in number, smooth and 

 glossy in texture, equally rounded at both ends, and double 



* This character is not of very much importance, as it varies in the 

 different species of Sand-Grouse. In the common Pin-tailed Sand-Grouse 

 {Pterochirus exusUts) the backward prolongation of the inter-maxillary 

 bones falls short of the horizontal line drawn between the posterior 

 margins of the nasal notches, so that in this species we see a typical 

 " schizorhinal " skull (Fig. 2). In Pallas' Sand-Grouse {Syrrhaptes para- 

 doxtis) the inter-maxillary processes reach this line and a perfectly inter- 

 mediate type ensues ; but in the Eastern Pin-tailed Sand-Grouse {P. 

 alchatus) they extend beyond, and practically a " holorhinal " form is shown 

 (Fig. 3)- 



