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themselves on little mounds and gaze on intruders, is noticed by all travellers. On the left, in the foreground, is one of the extraordinary pouched rats of America (Geomys bursarius). These are burrowing animals, feeding on roots; and the mouth is, as it were, double, the outer portion very wide and hairy, behind which is the small inner mouth. Its use may be to keep out the earth from the mouth while the animal is gnawing roots. A mouth so constructed is found in no other animals but in these North American rats. In the distance is a herd of bisons (Bison americanus), the typical beast of the prairies.

Birds.—This sub-region has many peculiar forms of birds, both residents, and migrants from the south or north. Among the peculiar resident species we may probably reckon a dipper, (Cinclus); Salpinctes, one of the wrens; Poospiza, Calamospiza, genera of finches; Picicorvus, Gymnokitta, genera of the crow family; Centrocercus and Pediocates, genera of grouse. As winter migrants from the north it has Leucosticte and Plectrophanes, genera of finches; Perisoreus, a genus of the crow family; Picoides, the Arctic woodpecker; and Lagopus, ptarmigan. Its summer, migrants, many of which may be resident in the warmer districts, are more numerous. Such are, Oreoscoptes, a genus of thrushes; Campylorhynchus and Catherpes, wrens; Paroides, one of the tits; Phænopepla, allied to the waxwing; Embernagra and Spermophila, genera of finches; Pyrocephalus, one of the tyrant shrikes; Callipepla and Cyrtonyx, American partridges. Besides these, the more widely spread genera, Harporhynchus, Lophophanes, Carpodacus, Spizella, and Cyanocitta, are characteristic of the central district, and two genera of humming-birds-Atthis and Selasphorus-only occur here and in California. Prof. Baird notes 40 genera of birds which are represented by distinct allied species in the western, central, and eastern divisions of the United States, corresponding to our sub-regions.

It is a curious fact that the birds of this sub-region should extend across the Gulf of California, and that Cape St. Lucas, at the southern extremity of the peninsula, should be decidedly more "Central" than "Californian" in its ornithology. Prof.

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