THE BATS OP NORTH AMEEICA. 171 



been consulted by Dr. Allen for tlie purposes of this Memoir, so that 

 he may be fairly said to have had at his disposal all the materials of 

 the three chief Zoological collections of North America. 



Dr. Allen commences his Memoir by an introduction, in which the 

 various types of modification assumed by the vertebrate skeleton, 

 with the object of adapting the animal to flight are discussed, and 

 diagrams are given, showing the bony structure of the wings in the 

 Bat, the Pterodactyle, the typical Bird, and the Archseopteryx. 

 He then proceeds to describe shortly the general structure of the 

 Chiroptera, and gives some particulars of their habits, of which, how- 

 ever, at present, our knowledge is very small. Dr. Allen then enters 

 upon the general subject of his work, heading it by an " artificial 

 Key to the Genera" of the Bats found within the limits of America, 

 north of Mexico, concerning which we may say a few words. As 

 in Europe, the Chiroptera met with in the northern parts of the New 

 "World mentioned, all belong to the insectivoroiis families of the 

 order. The true frugivorous Bats of the family Pteropodidse are, 

 we need hardly remind our readers, strictly confined to tropics of the 

 Old "World. There are found, however, within the limits to which 

 our author extends his work, representatives of three insect-eating 

 families of Chiroptera, which are here termed, MegadermatidcSy Noc- 

 tilionidw, and Vespertilionidce. 



The family with which Dr. Allen begins his Memoir has only one 

 representative in the North American Fauna. This is the Macrotus 

 Californicusy Baird, stated to be nearly allied to M. Waterhoimi, 

 Gray, of Cuba, Hayti, and the other "West Indian Islands. The 

 alliances of this genus appear to be rather obscure. Dr. Allen 

 refers it to the Megadermatidae, with which, however, it has probably 

 but a very remote connection. The Megadermatidse are a family of 

 Bats confined entirely to the Old "World. Although Macrotus has its 

 ears united together by a connecting membrane, there can be little 

 doubt that its true place is in the family PhyllostomatidsB — a group 

 peculiar to the tropics of the New AYorld, of which it forms a 

 northern outlier. 



The next family containing the naked-tailed Noctilionidse is like- 

 wise very feebly represented in the Nearctic Begion — one species only 

 — the Nyctinomus nasutus, a well-known and wide-ranging South 

 American form, occurring in different parts of the southern frontier 

 of the United States. The remaining Chiroptera treated of by Dr. 

 Allen — 18 in number, all belong to the insectivorous fjimily Yesperti- 



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