P R E F A C P:. 



Nearly thirty years have passed since the Monograph of the North 

 American Bats* api)eared as one of the series of miscellaneous publi- 

 cations of the Smithsonian Institution. Imperfect as it was, this me- 

 moir has remained the single work on the subject. The influence of 

 Prof. S. F. Baird is discernible throughout, and it is proper to say that 

 the opinions of species therein entertained were accepted by him. But 

 the changes in systematic zoology make it desirable that a new essay 

 be written. 



The monograph as it now appears is essentially new. It is not only 

 larger by reason of the addition of species, but the descriptions are 

 elaborated. Novel standards of comparison have been employed and 

 many anatomical details included in the introduction. 



The region occupied by the monograph (as in the original issue) is 

 that of North America, extended to the south as far as the boundary 

 line between the United States and Mexico. 



Since 18G4 two forms {Euderma maculata and Atalapha teliotis) have 

 been discovered. Two tropical genera {ArtibeKs and Fromops) and one 

 species ( Vcspertilio albescens) have been found to extend their northern 

 movements so as to be included in the United States. The chief acces- 

 sions have come in the form of geographical subspecies. Among these 

 occur Fromops perotis californicus, N'yctinotnus mucrotis neradensis^ 

 Vespertilio albescens melanorhinus, Vespertilio albescens affinis, Vespertilio 

 albescens evotis, YespertiUo nitidus ciUolahrum, Yespertilio nitklus ma- 

 cropus, and Vespertilio nitidus lomjicrus. 



In the accounts of the genera Vespertilio and Nyctinomus, which we 

 know to range southward over extended areas, the work is confessedly 

 incomplete, since the material available did not i)ermit of com^jrehensive 

 study. I felt indisposed to treat critically the descriptions of authors 

 of forms, which, in my judgment, demanded careful comparisons of types 

 and of extensive series of individuals, I can not pass judgment there- 

 fore upon the validity of tlie new species of Nyctinomus described by 

 Br. C. Hart Merriam [Kyctinomus femorosaccus and Xyciinomus moha- 

 vensis), nor of several new species of Vespertilio from Mexico which 

 have been described by other authors. 



*A Monograph of the Bats of North AnuTica. H. Allen, M. t)., assistant 8urgeoil 

 U.S. Army, Washington, D. C, 1864. 



