VERTEBRA! A.' 247 



Spermophilus. Haplodontiida. 



Castor (Beaver). Tamias. Haplodontia. 

 Pteromys (Flymg- 



Sciurida. Squiml). Ischyromyida. 



Arctomys (Marmot), iuras (Squirrel). *Ischyromys. 



Order V. CHIROPTERA. (Bats.) 



VOLITANTIA. 



Fore limbs with four prolonged ulnar digits, united by an 

 extension of the integument. Three kinds of teeth. One or two 

 pairs of pectoral mammae. 



The pollex (or thumb) is free, and not prolonged as are the 

 digits, and is alone furnished with a claw or nail. A membranous 

 skin extending from the lower part of the neck to the extremities 

 of the digits, and usually continued to the tail, forms a powerful 

 organ of flight [patagium]. The bones contain no air-cells as in 

 birds, nor is there any mesial crest to the sternum. The eyes are 

 small ; but the ears are often very large and, as well as the mem- 

 brane of the wings, are probably subservient to the sense of touch. 

 The nose, also, is sometimes furnished with peculiar membranous 

 expansions. In the tongue of the Phyllostomidae there is a pecu- 

 liar disposition of the terminal papillae, enabling it to act as an 

 organ of suction. These bats, it is well known, suck the blood of 

 other animals, man included. The vampyre ( Vampyrus spectrum) 

 is one of the worst. 



Bats are crepuscular or nocturnal and hibernate in cold cli- 

 mates. Except Pteropodidae, which are exclusively frugivorous, 

 they are nearly all insect-feeders. When at rest, they suspend 

 themselves by one of their thumbs, or hang head downwards, 

 holding on by their hind feet. 



The female bat brings forth one or two at a birth, which she 

 carries about with her. The young, in some species at least, are 

 born blind and destitute of hair. 



Six families are recognized ; but the genera and " subgenera " 

 are very numerous. Dobson divides them into two suborders 

 Megachiroptera and Microchiroptera the large and the small 

 bats respectively. There are some 500 species, of which about 17 

 are British. Our common bat is Vespertilio pipistrellus ; the 

 long-eared bat (Plecotus auritus) is also common ; V. murinus is 

 only a very rare straggler. 



