548 Beviews. [July, 



although it is published with a view to an increased demand for the 

 instruments he seeks to recommend, this in nowise lessens its value in 

 our estimation as a literary effort, and if successful, it will be doubly 

 productive of benefit to microscopical science. 



THE BATS OF NOETH AMEEICA* 



Bats, " the onely bird that suckleth its little ones," in the quaint 

 language of Holland, the translator of Pliny, exhibit the most com- 

 plete modification of the mammalian form for flying purposes. For 

 although there are flying lemurs (Galeopithecus), flying squirrels 

 (Pteromys), and flying opossums (Petaurista), in all these cases the 

 furred skin extends laterally from the sides of the body, and is 

 attached to the anterior and posterior extremities of the metacarpal 

 and metatarsal regions respectively, but is not associated with any 

 especial osseous framework, such as is afforded by the elongated 

 fingers of the bats. The bones of the Cheiroptera, too, do not com- 

 municate with the air, as do the bones of birds ; but they are of 

 extreme lightness and tenuity, the skeleton of the common brown 

 bat of North America (V. subulatus) weighing only eleven grains. 

 The skull, however, which in birds is light and toothless, is in 

 bats large and rounded, containing from 30 to 38 teeth, usually four 

 incisors in the upper and six in the lower jaw, canines, and molars 

 which never exceed (true and false) six above and six below on 

 either side. These differences in the number of the teeth form im- 

 portant characters in classification. To balance the weight of the 

 head, there is great development of the ribs, sternum, and scapula, 

 for the attachment of strong muscles of flight, as well as a long and 

 strong clavicle. The senses of hearing and of touch are, in bats, 

 remarkably developed, and each is accompanied by growths, which 

 are very characteristic of the Cheiroptera, viz. the enormous ears, and 

 the singular and grotesque leaf-like appendages situated upon the 

 nose. The ears, both externally and internally, are highly perfected. 

 The cochleae are disproportionately large, as compared with the size of 

 the semi-circular canals, the ampullae very large ; and to this osseous 

 framework for the reception of sound, is added a complicated auricle, 

 such as all insectivorous bats are provided with, and which is fre- 

 quently larger than the head, and of a great variety of shapes, which 

 are of great importance in classification. 



The dermal growths of the nose are situated about the nostrils, 

 and are either simple, upright, triangular folds of skin, or they may 

 be exceedingly complicated in structure. No North American bat, 

 with the exception of Macroticus Californicus, has such a develop- 

 ment. These appendages are reduplications of skin, and are not 

 related to the lining membrane of the nose, and it is doubtful whether 

 they hold a definite relation to the olfactory sense. They are pro- 



* 'Monograph of the Bats of North America.' By H. Allen, M.D., Assistant- 

 Surgeon, U.S.A. (Smithsonian Miscellaneous Collections.) 



