320 



DR. H. GADOW ON THE SPECIES OF RHEA. [MaV. 17, 



Tegumentanj System. 



Concerning the coloration of the plumage, Hh. macrorhyncha is 

 said to be distinguishable from Uh. americana " by its generally 

 browner colouring, and by the darker crown, which is nearly black " 

 (Forbes). Rh. darioini is characterized by its white-tipped feathers. 

 How far these differences are sul)ject to individual variation, and to 

 age, is not yet satisfactorih' known, owing to the scarcity of adult 

 specimens of Sh. macrorhyncha. 



One decidedlj' good distinguishing character is given by the scales 

 and the scutellation of the metatarsus. In Rh. darwini the distal 

 half of the front side of the metatarsus is covered by broad transverse 

 scutes, numbering about 20 ; whilst on the proximal half, the sides, 

 and the hinder aspect of this portion of the foot the featherless iute- 



Fig. 11. 



Median view of the left foot of Eh. darwini, diagrammatic, 

 fourth toe is not shown. 



The outer or 



gument is reticulated. The multangular reticulate Httle scutes are 

 thickest and largest on the " heel," and are gradually decreasing in size 

 towards the toes. The anterior dorsal surface of the toes is protected 

 as follows : — The middle (3rd) toe is covered by 23 transverse broad 

 scutes, which form the direct continuation of those of the metatarsus. 

 The inner (2ud) toe possesses only about 9-10, the outer (4th) toe 

 about 12 such scutes ; these are biggest near the claws or nails, and 

 gradually change into the reticulated structure which covers the 

 first phalanx of the inner and outer toes. 



In Rh. americana and Rh. macrorhyncha the front of the meta- 

 tarsus is covered with broad transverse scutes throughout its length, 

 like the dorsal sides of the toes. Rh. darwini represents in this respect, 

 like DromcBus and Casuarius, a lower stage than either Struthio or 

 the other Rheas, since for obvious reasons the formation of broad 

 scutes began distally, at the toes, and worked its way proximally 

 upwards. 



Geographical Distribution. 



The geograjihical distribution of the three species of Rhea known 

 at present seems to be the following : — 



Rh. americana ranges from Bolivia and the Province of Mattogrosso 



