106 DR. R. O. CUNNINGHAM ON RHEA. [Feb. 7, 



have picked up its characteristic white-tipped feathers in various 

 localities in the plains *. 



I regret that I have almost nothing to add to our knowledge of 

 the habits of Rhea americana, as it was but seldom that I noticed 

 live examples, and then, owing to their speed of foot, only for a few 

 minutes at a time. I can, however, corroborate the testimony of 

 Mr. Darwin with regard to the facility with which the species takes 

 to the water, one of the officers of the 'Nassau,' a very careful and 

 trustworthy observer, having on one occasion observed several in- 

 dividuals on the south of St. Jago Bay (Strait of Magellan) escape 

 from threatened danger by running into the sea. Further, I may add 

 that, although indiscriminate in its feeding like other members of the 

 tribe, it appears, in common with the Upland Goose (Chloephaga ma- 

 gellanica), to cherish a special predilection for the red berries of the 

 Empetrum rubrum, a plant very abundant on the grassy plains. 



Some months ago Mr. Sclater was good enough to place in my 

 hands for examination and comparison two nearly perfect skeletons 

 of Rhea americana and R. darwinii ; and I now venture to lay a few 

 brief notes on the subject before the Society. Both specimens were 

 those of females, that of Rhea americana having apparently belonged 

 to an adult bird, while that of R. darwinii bore unequivocal traces 

 of immaturity. It is necessary, of course, to bear this fact in mind, 

 as many of the differences observable are without doubt due to the 

 different ages of the individuals, while a certain number are possibly 

 only the result of individual variation, and others may probably with 

 justice be regarded as marks of specific distinction. 



Regarded in toto, the differences between the two skeletons are 

 comparatively slight, though perhaps not more so than those which 

 commonly obtain between closely allied species. In the following 

 observations, I would premise that it is not my intention to attempt 

 the very elaborate task of giving a full description of the osteology 

 of the two species, as to do that in a complete and satisfactory 

 manner would have necessitated the examination of a much larger 

 number of specimens than I have had at my command, but to 

 content myself with noting those points which appear to be of the 

 most salient character. 



Cranium. — Beginning with the cranium, I may remark that its 

 general contour is very much the same in both species, though 

 certain minute marks of distinction between the individual bones are 

 recognizable on a careful inspection. Thus in the cranium of the 

 specimen of Rhea darwinii (in which nearly all the bones are still 

 unanchylosed) the vertical ridge on the supraoccipital is considerably 

 more elevated than in R. americana, and the portion of the hori- 



* When Dr. Adolf Booking, in his interesting " Monographic des Nandu oder 

 sudamerikanischen Strausses," in Wiegmann's Archiv for 1863 (for a reference to 

 which I am indebted to Mr. Sclater), speaks of R. americana and R. darwinii 

 as climatic varieties comparable with those of Pcrdix cinerea, it is difficult to 

 avoid the conclusion that ho has never carefully examined specimens of the two 

 birds ; and his hypothesis is disproved by the fact of their occurring in the same 

 district. 



