OF THE TONGUES OF THE MAMMALIA. 



117 



mouth, and a piece of the anterior part of the dorsum appears to 

 take its place. 



Median Fissures and Ridges. 



A median fissure may extend backwards over the dorsum for 

 a variable distance from the apex, and it may be continuous or 

 interrupted. It may be merely a line of separation between two 

 lateral masses of conical papillae, as in the Californian Sea Lion, 

 or it may indent the mucous membrane to a variable depth. In 

 the Negro Tamarin and the Stoat, the tongue is small, and the 

 median fissure, which is deep, especially in the former, is a marked 

 feature. 



The median fissure may be restricted to the front, middle, 

 or back of the tongue, aini it may be narrow throughout, 

 or widen from before backwards. 



In some of the Lemurs, Marmosets, and Carnivora, there may 

 be a median ridge instead of a sulcus. 



Text-figure 7. 



/'''■^CfloUES SPOTTED C/>Vy MANMROO AYE -AYE 



Different foniis of mesial furrows find ridges on the inferior surfoce of the tonsjue. 

 Fissures are shown in the Macaques and Spotted Cavy, and ridges in the 

 Kangaroo and Aye-Aye. 



The inferior surface, like the dorsum, may possess a median 

 fissure or ridge, but either is restricted to the free part. The 

 muscles prevent it going any farther back. It is narrow and deep, 

 or broad and shallow, a.nd it may end abruptly, or open into a 

 triangular depression into which the frenum passes (text- fig. 7). 



In Galeopithecus^ and the Spotted Cavy, small transverse 

 fissures pass horizontally out for a variable distance from the 

 posterior extremity of the median furrow. Again, the tongue of 

 GaleopithecurS has small lateival fissui-es passing inwards from the 

 marginal lobulations. 



In the Kangaroo, as in other Marsupialia, there is a firm, hard 

 median ridge passing back from the apex to the frenum, and, in 

 the Aye -Aye, a mediaii ridge runs along the surface of the 

 sublingua, but it is not the same as that described above. It 

 represents the iytta. 



Transverse Ridges and, Fissures, 



Transverse ridges and fissures are of two kinds — artificial 

 and real, — the former appearing in preserved specimens as the 



