20 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 



ridse the first dorsal vertebra is fused with the last cervical. In the 

 Rhinolophidse the seventh cervical vertebra and first dorsal are so 

 completely fused that their boundaries can not be detected ; this com- 

 pound vertebra is fused with the first rib, which in turn is fused with 

 presternum. The second rib fuses with first at about its point of 

 attachment with presternum, to which it is joined throughout the rest 

 of its course by a thin sheet of bone. At first sight, therefore, the 

 presternum appears to be enlarged to a broadly crescentic plate 

 applied to mesosternum at middle of its convex posterior border. 

 The original elements of this mass, though, perfectly fused, can still 

 be distinguished. In the Hipposideridse the strengthening process 

 attains its highest degree of perfection. Here the general structure 

 is as in the Rhinolophidse, but the fusion of the first and second ribs 

 involves the entire bone to and including the corresponding dorsal 

 vertebra?. A solid ring is thus formed, including three vertebrae, 

 two ribs, and the presternum, the elements indicated by a slit- 

 like vacuity between the upper halves of the ribs, a small median 

 space between the two dorsal vertebra?, and two minute roundish 

 apertures in the region corresponding to space between horizontal 

 arm of presternum and sternal portion of second rib. The mechanical 

 need for this remarkable strengthening in bats of this size is by no 

 means apparent. 



Teeth. 



Though much has been published concerning the teeth of bats, par- 

 ticularly by Winge," 1 the subject is still by no means exhausted. This 

 is especially true of the modifications of the various cusps of the per- 

 manent cheek teeth, which have hitherto received little attention. 

 Before passing to this more important aspect of the dentition, how- 

 ever, a few words on the milk teeth and the tooth formula may not be 

 out of place. 



MILK DENTITION. 



The peculiar and very highly specialized milk dentition of bats 



has long been known in a general way, but the material has not yet 



been brought together for a complete study of its variations. The 



largest number of milk teeth that has been observed is 22, with the 



, - 2 3. 1. 1 2 . 2 - 2 1-1 2 - 2 „ x . A . . 



formula: 1 ^ g ^ 1 ^ («w g _ g , mc 1 _ v mp _ 2 =22). As this 



is present in Myotis, a genus with the maximum number of per 7 

 manent teeth, it probably represents the complete set. It also occurs 



in Eptesicus, in which the corresponding portion of the permanent den- 



_ g 3_ j_ 4. 



tition is jo 3 1 ' _ o _ 4 an< i in Lasiurus with the permanent teeth 



ajorfundne og nulevende Flagermus (Chiroptera) fra Lagoa Santa, Minas 

 Geraes Brasilien, 1892, pp. 56-58. 



