Cheiroptera (BATS)

Order of deciduate-placental mammals po e ing true powers of flight, to effect which a patagium, including the tail and limbs and the fingers of the hand (except the thumb), is always present. The chest is strong with a sternal keel, and the scapula is large for the attachment of the muscles principally concerned in flight. The bones of the arm are long, especially the radius, the ulna is rudimentary. The metacarpals and phalanges included in the web are extremely long, the index digit sometimes consists of the metacarpal only. The medius is the longest digit. None of these po e claws as do the thumb and toes. The fibula is incomplete. A long spur or calcar extends backward from the oscalcis for supporting the web near the tail. The organs of vision are not well developed, and bats fly usually at night. The ears are large, but touch is the sense most developed, blinded bats fly as well as others, avoiding obstacles. During the day they retire to caves and crevices, where they hang suspended by the hind feet. In temperate and cold regions they hibernate. They walk with difficulty, and are not as active in flight as most birds. They have one or two young at a time, which are carried with them during flight and are suckled by a pair of pectoral mammæ. They first appear in the Eocene, but offer no special peculiarities. The dentition is complete. There are two groups. See BAT.