MOUTH OF MAMMALS. 387 



have similar cheek-pouches. The roof of the mouth between 

 the incisors and molars is narrow and ridge-like : as it expands 

 posteriorly it is commonly beset with two rows of hard oblique 

 rido-es. In no mammalian order is the food so much reduced by 



O 



mastication as in Rodents, and many of them show concomitant 

 modifications of the fauces ; such as the constriction of the soft 

 palate in the Capybara, reducing the communication between the 

 mouth and pharynx to a small aperture. In Capromys the upper 

 lip is furrowed longitudinally, but not bifid. On the middle line 

 of the palate, between the incisors and molars, are three distinct 

 hard white tubercles : the first, the largest and most prominent, 

 is situated about half-an-inch behind the incisors; the second, 

 which is the smallest of the three, is at a distance of three lines 

 from the former ; and immediately behind it is the third. On each 



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side of the first tubercle there is a softer one situated on the 

 margins of the upper lip. 



The gape of the mouth is wide in insectivorous Cheiroptera. 

 Some bats have a modification of the integument for an analogous 

 office to the cheek-pouches in a part of the body remote from 

 the mouth : the skin extended from the hind-legs to the incurved 

 tail (interfemoral membrane) forms a bag into which flies are 

 beaten, inclosed, and stored. The frugivorous kinds have not 

 this structure. 



In Nycteris two converging ridges of the lower lip inclose a 

 triangular prominence of the upper lip. In Otoops the upper lip is 

 transversely grooved. In Noctilio it is dependent. The palate is 

 transversely ridged, the hinder ones usually divided by a medial 

 cleft. The tongue can be protruded far in Cheiroptera ; and, when 

 retracted, usually shows transverse (Mormoojjs) or oblique foldings 

 of the dorsum : the minuteness or absence of incisors permits 

 protrusion even when the molars are in a state of apposition. Bats 

 use the tongue in lapping ; also in licking off the juice of fruits, as 

 e.g. in the tropical Phyllonycteris. The tip of the tongue is spinulose 

 in Rhinopoma. In the Vampire (Desmodus, Phyllostoma) the ter- 

 minal papillae resemble wart-like elevations, so arranged as to 

 form a circular suctorial disk when they are brought into lateral 

 contact by the action of a set of muscular fibres thereto adapted. 

 Some bats (Saccolaimus) have a gular pouch : in Molossus this 

 seems to be sexual, and is peculiar to the male. 



In the order Bruta, the mouth is remarkably short in the Sloths, 

 and attains its maximum of length and narrowness in the Ant- 

 eaters in which it seems to be mainly a sheath for the retracted 



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