19 



VIII. PEOBOSCIDEA (Elephants).— Mammals in which the nose is 

 prolonged into a long double-barrelled prehensile trunk (proboscis). Thick 

 skin almost hairless. The incisors form tuslts (ivory), and are without 

 enamel. Molars tioenty-four altogether throughout life, but never more than 

 eight present at a time. Five hoof-covered digits on each foot. Skull is 

 modified to carry the tusks by development of large air spaces in the bones. 

 Herbivorous. Placenta deciduate and zonary. e.g. Indian Elephant (parallel 

 enamel ridges on the molars). African elephant (lozenge-shaped enamel 

 folds on the crowns of the molars). 



IX. EODENTIA (gnawing Mammals). — Largest order of mammals. 

 Very old and widely distributed group. Dentition adapted to gnawing, 

 and is exceedingly characteristic. Incisors are chisel-shaped, and consist of 

 hard enamel in front, and less hard dentine behind, so that a permanent 

 edge is preserved. Canines absent. Long gap (diastema) between the incisors 

 and the premolars. Molars have flattened croitms with ti'ansverse enamel 

 folds. Stomach simple, but intestine very long (as in herbivorous animals 

 generally). Condyles of lower jaw elongated longitudinally, so as to admit 

 of longitudinal motion. Placenta discoidal deciduate. 



1. DuPLioiDBNTATA (Double-toothsd). — Incisors 2 upon 1. e.g. Lepus 



(Babbit). 



2. SiMPLiciDENTATA (Single-toothed). — Incisors 1 upon 1. e.g. Squirrels, 



Mice, Beavers, "flying" Squirrels, Porcupines, Guinea-pigs. 



[Hyraooidea, a small rabbit-like group of one genus, may be considered 

 as a sub-group of Rodentia.] 



X. INSECTIVOEA (Insect-eaters). — Plantigrade terrestrial mammals 

 of small size. Digits on hind and fore limbs all clawed. Long tapering 

 snout. Canines small or absent. Molars sharp pointed. Clavicles well 

 developed. Placenta discoidal deciduate. Feed on insects, worms, and 

 small animals. e.g. Hedgehog (Erinaceus), Mole, Shrew (the smallest 

 mammal — about two inches long). Flying Lemur (frugivorus and arboreal). 



XL CHEIROPTEEA (hand-winged).— The only true flying mammals 

 (other so-called flying mammals merely take long leaps). The fwe limbs 

 are modified for flight. The flying membrane extends between the limbs 

 and the side of the body, and between the elongated fingers of the fore 

 limb. Sternum is keeled for attachment of flying muscles. Clavicles 

 well developed. Dentition complete. Incisors smaller than the canines. 

 Mammae thoracic. Mostly nocturnal, hence eyes are poorly developed. 

 Placenta discoidal. 



1. Mbgachieoptera (great bats). — Fruit-eating bats. e.g. Pteropus 



(flying fox). Shores of Indian Ocean. 



2. MiCBOCHiEOPTERA (small bats). — Insect-eating or blood-sucking bats. 



Universal distribution, e.g. Common Bat (Vespertilio), Vampyre 

 Bat. 



