736 



Comparative Morphology of Chordates 



Subclass III. Placentalia 



Order 4: INSECTIYORA. Small, including the smallest of mam- 

 mals. Notably lacking in highly specialized characteristics except in 

 some arboreal or burrowing species. Dentition complete, but teeth of 

 the several types not strongly differentiated from one another: mainly 

 insect-feeding. Usually five digits on each foot; digits bear claws; loco- 

 motion plantigrade. Uterus bicornis. Cerebral cortex smooth. 



Examples: Shrew (Sorex); tree shrew (Tupaia); mole (Talpa); 

 hedgehog (Erinaceus), with a protective coat of sharp spines re- 

 sembling those of the porcupine, a rodent: (Figs. 543-545). 



Distribution: Both Eastern and Western Hemispheres, but not 

 in South America and not in Australia, New Zealand, and adjacent 

 islands. The hedgehogs occur only in the Eastern Hemisphere. 



Order 5: DERMOPTERA. Arboreal mammals having, on each 

 side of the body, a broad fold of skin extending from the neck to the 

 forelimb, from fore- to hindlimb, and behind hindlimb to tail (Fig. 

 546). The feet, with digits webbed, project freely beyond the edge of 

 the fold. By spreading the "flying" membranes, the animal is enabled 

 to make long sailing leaps. The brain is of primitive type. In general 

 anatomy these animals resemble insectivores and also the more primi- 

 tive primates (lemurs). 



This Order contains only the "flying lemur," or colugo, Galeo- 

 pithecus, of the East Indies. 



Fig. 543. Common shrew. Sorex vulgaris, (Courtesy, Flower and Lydekker: "Intro- 

 duction to the Study of Mammals," London, A. & C. Black. Ltd.) 



