1885.] DR. H. GADOW ON THE SPECIES OF RHEA. .321 



(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. macrorhynelia has been found in the Provinces of Pernambueo 

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

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

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

 HI Guiana is therefore improbable. As Bh. 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-ran o-es] 

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



Summary. 



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



„ , „ -ff^^« americana. Eh. maororhynclia. Rh. darwini. 



Wumber of cervical 



vertebrae 15 16 15 



^^'•^ long long short. 



^!^^«1,.---,- shorter shortest longest. 



Hind limb shorter longer 



^?f shortest longer longest. 



^r-,, , , longest bill shortest bill. 



"^"ll broad narrow broad. 



Metatarsus with transverse scutes through its length, scutes on distal 



, , . , half only. 



Ainbieus muscle ... typically developed apparently sub- 



ject to fre- 

 quei:t ujodi- 

 ,„ 11. fications. 



Iracheal rings greatest number smaUestnumber. 



(jreneral coloration 



of plumage ■ generally darker mo,st of the fea- 



than Bh. ameri- thers with 

 cana, especially white tips. 

 _ on the head. 



^^oitat Southern half of Xoi-th-eastern South-eastern 



South America. Brazil. South Ame- 



rica. 



This tabular arrangement shows that Darwin's Bhea 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-vertel)me of Rh. macrorhyncha (the best name 

 for which would be that of the lony-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 Khea as three equivalent 



