1885.] 



DR. H. GADOW ON THE SPECIES OF RHEA. 



.121 



(Villa Bella and Cuyaba) through Paraguay across the Parana into 

 Uruguay. Its headquarters appear to be the pampas of Argentina, 

 ■whence it extends southwards to the Rio Negro of Patagonia. 



Rh. darwini seems to be restricted to the eastern half of Patagonia 

 and to South-eastern Argentina; about the Rio Negro of Patagonia 

 both species occur together. 



Rh. macrorhyncha has heen found in the Provinces of Pernambuco 

 and Bahia. Its north-westward and westward range is probably 

 limited not by the Amazons and its enormous tributaries, but by the 

 broad thick belt of forest of the Amazonian subregion. Its occurrence 

 in Guiana is therefore improbable. As Rh. americana does not seem 

 to occur in the South-eastern provinces of Brazil, "probably the 

 barrier between the two species is a continuously wooded country 

 [and I should add the numerous low but rough mountain-ranges] 

 between that district and the Sertoes de Bahia" (Forbes). 



Summary. 



The chief differences between the three species are the following : — 



Rhea americana. Rh. macrorhyncha. Rh. darwini. 

 Number of cervical 



vertebraj 15 16 1.5. 



Neck long long short. 



Hand shorter shortest longest. 



Hiud limb shorter longer. 



Toes shortest longer longest. 



BlU longest bill shortest bUl. 



Skull broad narrow broad. 



Metatarsus with transverse scutes through it.^ length, scutes on distal 



lialf only. 

 Ainbiens muscle .. . typically developed apparently sub- 



ject to fre- 

 quci'.t modi- 

 fications. 



Tracheal rings greatest number smallest number. 



General coloration 



of plumage ' generally darker most of tlie fea- 



than Rh. amcri- thers with 

 cana, especially white tips, 

 on the head. 



Habitat Southern half of North-eastern South-eastern 



South America. Brazil. South Ame- 



rica. 



This tabular arrangement shows that Darwin's Ehea differs con- 

 siderably from the other two species, whilst the latter offer apparently 

 few important characters for separation. However, no matter if the 

 number of the neck-vertebrae of Rh. macrorhyncha (the best name 

 for which would be that of the long-necked or slender-headed Rhea) 

 be a constant character or not, the differences in the proportions of 

 the skulls afford an anatomical character just as good as those 

 which induce us to consider Rh. darwini a so-called good species. 

 If we thus consider the three forms of Rhea as three equivalent 



