_Hirundo cinerea_, Gmelin, is a native of Tahiti and of the Marquesas Islands, but has not to our knowledge ever been detected on the continent of North America. It belongs to the genus _Collocalia_, Gray. The Bank Swallow (_Cotyle riparia_) also was named _Hirundo cinerea_ by Vieillot, but is given in Mr. Ord’s list as distinct from the present. 5. Hirundo rupestris. “The Rock Swallow.” Ord, in Guthrie’s Geog., II. p. 317. (1815.) This name also occurs in Mr. Ord’s Catalogue, cited above. _Hirundo rupestris_, Scopoli, inhabits Europe and Asia, but we have never been informed of its appearance in America. It is a _Cotyle_. We have now given all the species of Swallows known or supposed to inhabit the continent of America, north of Mexico. As stated in a preceding page, Swallows are found in all countries except the Arctic regions, and are, so far as known to naturalists, birds of very considerable similarity of habits and of general characters. The various groups usually regarded as sub-families and genera are perhaps as easily distinguished in this family as in any other of the entire class of Birds, and it is one in which it is remarkable that almost every country produces species which belong to the genus (_Hirundo_) which is the type and apparently primary form of the family, besides forms peculiarly its own. The types of great groups apparently more pre-eminently characterize the ornithology of Europe than that of any other division of the globe. In other words, Europe appears to produce the greatest number of species of birds exhibiting the fullest development of the especial characters of the groups to which they belong. It is very remarkable, too, that species are found almost throughout the world slightly aberrating, as it were, from European forms, or as though a typical form was produced with a greater or less degree of imperfection. Of this description of birds, the various species nearly allied to the House Swallow of Europe (_Hirundo rustica_), are a striking illustration. The American _Hirundo rufa_, and several Asiatic and African species, are only distinguished from that bird by characters of inferior value in specific identification. Australia, too, produces species, which, though apparently farther removed, are still similar. There are many other European birds which appear to occupy the same relative positions. The Goatsucker, Raven, Crow, Jay, and Peregrine Falcon, are instances. Of the European Conisostral birds, nearly every species has nearly allied forms in other regions.