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ZOOLOGY OF THE TOYAGE OF THE BEAGLE. 
R. Darwinii. R. Americana, 
inches inches 
Length of beak, from edge of membrane at base to the apes ... 2 2| 
Length, from anterior margin of eye to apex ...... 
Width of upper mandible, measured across middle of nostrils . . . 1-^ 
The skin round and in front of the eyes is less bare in R. Darwinii; and 
small bristly feathers, directed forwards, reach over the nostrils. The feet and 
tarsi are nearly of the same size in the two species. In the R. Darwinii, short 
plumose feathers extend downwards in a point on the sides of the tarsus, for about 
half its length. The upper two-thirds of the tarsus, in front, is covered with 
reticulated scales in place of the broad transverse band-like scales of the R. Ameri- 
cana ; and the scales of the lower third are not so large as in the latter. In the 
R. Darwinii the entire length of the back of the tarsus is covered with reticulated 
scales, which increase in size from the heel upwards : in the common Rhea, the 
scales on the hinder side of the tarsus are reticulated only on the heel, and about 
an inch above it ; all the upper part consisting of transverse bands, similar to 
those in front. 
The first notice I received of this species was at the Rio Negro, in Northern 
Patagonia, where I repeatedly heard the Gauchos talking of a very rare bird, 
called Avestruz Petise. They described it as being less than the common ostrich 
(which is there abundant), but with a very close general resemblance. They 
said its colour was dark and mottled, and that its legs were shorter, and feathered 
lower down than those of the common ostrich. It is more easily caught by the 
bolas than the other species. The few inhabitants who had seen both kinds, 
affirmed that they could distinguish them apart, from a long distance. The eggs, 
however, of the small species appeared more generally known, and it was 
remarked with surprise, that they were very little less than those of the common 
Rhea, but of a slightly different form, and with a tinge of pale blue. Some eggs 
which I picked up on the plains of Patagonia, agree pretty well with this descrip- 
tion ; and I do not doubt are those of the Petise. This species occurs most rarely 
in the neighbourhood of the Rio Negro ; but about a degree and a half further 
south they are tolerably abundant. One Gaucho, however, told me he distinctly 
recollected having seen one, many years before, near the mouth of the Rio 
Colorado, which is north of the Rio Negro. They are said to prefer the plains 
near the sea. When at Port Desire in Patagonia (Lat. 48°), Mr. Martens shot an 
ostrich ; I looked at it, and from most unfortunately forgetting at the moment, 
the whole subject of the Petises, thought it was a two-third grown one of the 
common sort. The bird was skinned and cooked before my memory returned. 
But the head, neck, legs, wings, many of the larger feathers, and a large part of 
the skin, had been preserved. From these a very nearly perfect specimen has 
