564 



CHORD AT A 



Order II. Insectivora. 



Of all living mammals the inscctivores stand nearest to the primitive type, 

 the order dating back to the eocene. The sharp-pointed teeth (sectorial), 

 adapted for insect food vary greatly in number in the different families (moles, 



^iiil; shrews, Iil;|), as also does the replace- 

 ment, since many forms retain the milk denti- 

 tion for a long time or never lose it, while the 

 shrews lose it very early. They have the process 

 at the angle of the lower jaw, a primitive brain, 

 a uterus bicornis or one divided throughout. 



, .. 6l , skull of Sorex (from There are frequently scales on the tail among 

 Ludwig-Leunis). the hairs; the clavicle is present; usually five 



clawed toes. . The animals which as a rule are 

 small with soft hair, usually have a proboscis-like, tactile snout. 



The ERINACIDVE, Old World hedgehogs, are spined; the SORICID.E, or shrews 

 (Sorc\ * Blarina*), are mouse-like, as are the allied TALPID^:, or moles (Scalops* 



FIG. 613. Skeleton of bat (after Brehm). 



( 'imdylnra* star-nosed mole), which burrow in the earth and have the eyes more 

 or less rudimentary. Some authors place here Galcopilliecits of the East Indies, 

 which has a similar membrane and sailing powers as the flying squirrels. It 

 also resembles the bats and lemurs. 



Order III. Chiroptera. 



The bats are the only mammals which actually fly, and this at once charac- 

 tcri/.es them. The flying membrane (pata^iiun), a thin fold of skin, begins at 

 the tail, includes the lower extremities to the foot, and extends thence to the 

 fingers, leaving the thumb free. Fingers 2-5 are enormously elongated and 

 support the membrane. Since flight requires strong muscles, the sternum 

 develops a small keel for the attachment of the large pectoral muscle. In 

 connexion with the Hying powers the clavicle is strong. The patagium is very 

 sensitive; blinded bats ran fly among all kinds of obstacles without disturbing 

 them. The enormous ear conchs and a noticeable nose leaf, widely distributed 

 through the group, also have marked tactile powers. In the pectoral position 



