420 DESCRIPTION OF [November 



cies, and he hinted that it might at some future period 

 become the type of a new genus. This proper suggestion 

 is now proved to be correct, by the discovery which I 

 have made of three other species having the same singu- 

 lar character in the lower hp. I have therefore thought 

 needful to establish such a new genus, which shall at 

 present consist of four species; but I am certain that it 

 contains many more, which may gradually be detected, 

 when our rivers shall be more fully explored. I would 

 have called it Maxillingua, if generic names of many com- 

 pound Latin words were not to be avoided, according to 

 the correct Linnean principles. Glossognathus having the 

 same meaning in Greek, appears to me rather harsh, and 

 for the sake of euphony I have preferred Exoglossum, 

 which means outside tongue, and applies quite as well to 

 the whole genus, wherein the middle lobe of the lower 

 jaw assumes the appearance of a tongue jutting out of 

 the mouth. This genus may be distinguished at first 

 sight, by this striking character, from any other of the 

 same family. 



ENUMERATION OF THE SPECIES. 



1. Exoglossum Lesurianum, Cyprinus maxiUin' 

 gua, Lesueur. S^e his description, page 85, of this 

 Journal. The specific name of maxillingua cannot be 

 retained, because it applies to all the species of the 

 genus: it may rather be employed as a designation for 

 the section of the genus furnished with a trilobated lower 

 Jaw. 



2. Exoglossum macropterum. PI. 17, fig. 3. 



Head nearly square, forehead truncate, tuberculated, 



