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, ^Vt 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 Hipposideridae the strengthening process 
attains its highest degree of perfection. Here the general structure 
is as in the Rhinolophidae, but the fusion of the first and second ribs 
involves the entire bone to and including the corresponding dorsal 
vertebrae. 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 vertebrae, 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, a 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, Avhich 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 
formula: ^ 9 g ^ ^ (rm g me ^ mp ^——^=22). As this 
is present in Myotis , a genus with the maximum number of per- 
manent teeth, it probably represents the complete set. It also occurs 
in Eptesicus , in which the corresponding portion of the permanent den- 
— 2 3. 1. 4 
tition is } 2 3 * l‘ - 9 - 1 and * n -^ as ^ uru8 with the permanent teeth 
aJorfundne og nulevende Flagermus (Chiroptera) fra Lagoa Santa, Minas 
Geraes Brasilien, 1892, pp. 56-58. 
