Glass 6. Mammalia. Order 6. Proboseidea. 



511 



common membrane. The snout is produced into a long trunk, 

 bearing tbe nares and, in the Indian Elephant, a finger-like process 

 at the tip; it is a prehensile organ, and conveys food (plants) to the 

 mouth ; water is sucked up into it and squirted into the mouth, 

 towards which the tip can be directed. The pinnse are large 

 dependent flaps. The mammse (two) are close to the forelegs. The 

 head is borne upon a short thick neck, and is of colossal size; 

 the cranium small ; extensive air sacs in the bones of the head. 

 Incisors absent from the lower, one on each side in the upper 

 jaw; this, in the males especially, is modified to form a long tusk 

 which is curved forwards, and is practically devoid of enamel; it 

 projects some distance from the mouth, and grows continuously 

 throughout life. Canines are absent. The molars are large, with 

 high crowns and short roots ; the crown is made up of a varying 

 number of compressed transverse plates coated with enamel, and 



Fig. 409. Molar teeth in longitudinal section. A, B different species of Mastodon, C 

 Elephant ; diagrammatic, cement removed ; d dentine, e enamel, k pulp cavity, r root. — 

 Orig. 



bound together with an abundant supply of cement. There is 

 never more than one, or at most, two, teeth in use at the same time 

 in each half of the jaw : as one tooth is worn away another comes 

 forward and gradually takes its place ; the anterior end comes into 

 use, whilst the posterior part is still within the jaw : it is therefore 

 worn away first, so that at last only the posterior end remains. 

 Altogether sis molars appear in this way on each side ; the first to 

 arise being the smallest.* There are only two living species : the 

 Indian Elephant {E. indicus) , with the molar-plates numerous and 

 much compressed ; with relatively small pinn^ j it is both wild and 



* The six molars of the Elephant are : dp', df,', dp', m}, m?, m-' ; the premolars are 

 wanting in living forms, but rudiments oocuj- in an extinct species, and alsQ in 

 M^todou, 



