ORDERS OF MAMMALIA. 313 



thus formed often includes the tail, and is nearly or quite 

 naked or destitute of hairs on both sides. It is used as an 

 organ of true flight, and, in accordance with this, there are 

 well-developed collar-bones (clavicles), and the breastbone is 

 furnished with a ridge for the attachment of the pectoral mus- 

 cles. Of the fingers of the hand at least three are destitute 

 of nails. The mammary glands are placed upon the chest. 

 Teeth of three kinds are always present, and the canines are 

 always well developed. 



The Bats are all twilight-loving or nocturnal animals, and 

 they are the only Mammals which possess the power of true 

 flight, though several others can make extended leaps from 

 tree to tree. The eyes are small, but the ears are very large, 

 and their sense of touch is most acute. During the day they 

 retire to caves or crevices in rocks, where they suspend them- 

 selves by the short thumbs, which are provided with claws. 

 In their flight, though they can turn with great ease, they are 

 by no means as rapid and active as the true Birds. The tail 

 is sometimes very short, sometimes moderately long, and is 

 usually included in a continuation of the " patagium," which 

 extends between the hind-legs. The body is covered with 

 hair, but the patagium is usually nearly or quite hairless. 

 Most of the Bats hybernate. 



The Cheiroptera are conveniently divided into the two 

 sections of the Insectivorous and Frugivorous Bats. In the 

 first section are all the bats of temperate climates, most of 

 which are of very small size, and all of which live upon in- 

 sects. Here also belong the great Vampire-bats (Phyttosto- 

 midce) of South America. In the second, or fruit-eating sec- 

 tion of the Cheiroptera, are only the Fox-bats (Pteropidce), 

 which are especially characteristic of the Pacific Archipelago, 

 inhabiting Australia, Java, Sumatra, Borneo, etc., but occur- 

 ring also in Asia and Africa. They are among the largest 

 of the Bats, one species the Pteropus edulis or Kalong at- 

 taining a length of from four to five feet from the tip of one 

 wing to the tip of the other. 



ORDER XII. INSECTIVORA (Lat. insectum, an insect ; voro, 

 I devour). The twelfth order of Mammals is that of the In- 

 seetivora, which comprises a number of small animals, very 

 similar in many respects to the Rodents, but wanting the 

 peculiar incisors of that order, and also being provided with 

 clavicles. All the three kinds of teeth are present, but the 

 dentition is very various, and the only common character is 



