484 Mr. N. A. Vigors oh the Natural Affinities 



The chief genera comprised in the Struthionida are the RAca, 

 Briss., which unites this family with the last; the Strut hio, Linn., 

 which having but two toes, and thus carrying the character of 

 the group to the extreme, may be considered the type ; the 

 ('asuarius, Briss., Dromiceius, Vieill., and Otis, Linn. Consi- 

 derable doubts have arisen as to the present existence of the 

 liinnean Didus ; and they have been increased by the consi- 

 deration of the numberless opportunities that have latterly oc- 

 curred of ascertaining the existence of these birds in those situa- 

 tions, the Isles of Mauritius and Bourbon, where they were 

 originally alleged to have been found. That they once existed 

 I believe cannot be questioned. Besides the descriptions given 

 by voyagers of undoubted authority, the relics of a specimen 

 preserved in the public repository of this country bear decisive 

 record of the fact. The most probable supposition that we can 

 form on the subject is, that the race has become extinct in the 

 before-mentioned islands, in consequence of the value of the 

 bird as an article of food to the earlier settlers, and its incapa- 

 bility of escaping from pursuit. This conjecture is strengthened 

 by the consideration of the gradual decrease of a nearly conter- 

 minous group, the Otis tarda of our British ornithology, which, 

 from similar causes, we have every reason to suspect will shortly 

 be lost to this country. We may, however, still entertain some 

 hopes that the Didus may be recovered in the south-eastern part 

 of that vast continent, hitherto so little explored, which adjoins 

 those islands, and whence, indeed, it seems to have been origi- 

 nally imported into them. I dwell upon these circumstances 

 with more particularity, as the disappearance of this group gives 

 us some grounds for asserting, that many chasms which occur 

 in the chain of affinities throughout nature may be accounted 

 for on the supposition of a similar extinction of a connecting 

 species. Here we have an instance of the formef existence of 



a species 



