Temminck's Monographies de Mammalogie. 459 



than three should be merely copied from the plates in the Aunales 

 du Museum. M. Temminck, who declaims so loudly against com- 

 pilatioDj ought surely to have had recourse for his illustrations to 

 those ample stores of original materials which he has at his 

 disposal, and which would have supplied him with more than 

 twice the number of yet unfigured species. 



The sixth Monograph is devoted to another genus of Cheiroptera^ 

 the Dysopes of Illiger, which is synonymous with the Molossus of 

 M. Geoffroy Saint-Hilaire, and also, according to M. Temminck, 

 with the Nyctinomus of the latter authour. To establish the 

 identity of these genera, the distinction of which rested only on 

 the number of the incisor teeth of the lower jaw, numerous facts 

 are detailed tending to prove that this character varies according 

 to the age of the individual. Those of the upper jaw are also 

 variable in number, and the dentary formula, as far as the in- 

 cisors are concerned, may be either i, f, |, 4? or even ^. The 

 privation of the lower incisors takes place progressively. The base 

 of the canine teeth becomes developed, and by its enlargement the 

 incisors are successively displaced ; the projecting lateral points 

 of the canines eventually performing the office of incisors, and 

 being opposed, while engaged in taking food, to the incisors of 

 the upper jaw which are worn away by them. M. Temminck de- 

 scribes these facts as they have been witnessed by him in seven of 

 the eleven species which have fallen under his observation. In 

 order to show the mode of proof adopted by him, we follow him 

 through one of the instances which he has adduced, that of the 

 Dys, nasutus^ described by M. Isidore Geoffroy Saint-Hilaire as 

 the Nyctinomus Brasiliensis. In one young individual of this 

 species there existed, in the lower jaw, six incisors ; in another, 

 five, three being on one side, and two on the other ; in a third, 

 four only, and in the upper jaw of this specimen, three incisors, 

 with the alveolus, partly closed, of a fourth ; in about thirteen 

 other specimens, the number of incisors in the lower jaw was 

 four ; and in two full-grown individuals there were only two. 

 The entire absence of even these has been found in i\\e Dys, 

 obscurus. Another observation will carry almost beyond the pos- 



