DD THE SKULL AND TEETH OF ECTOPHYLLA ALBA. 
One of the most marked characteristics of the teeth of fruit-eating bats is the dis- 
position for the loss of cusps in the molar teeth. This takes place without intermediate 
grades so far as is known. In two of the three subdivisions of the Phyllostomide it 
occurs as exceptions to the rule—Hemiderma in the Vampyri and Phyllonycteris in the 
Glossophaginee, but is the rule rather than the exception in the Stenodermine. In the 
Pteropodide the tendency to the loss of cuspidation is the rule, the genus Pteralopex 
being the only exception. Such abrupt variation within the limits of small groups indicates 
that the tendency to external specialization has weakened the type and exposes it under 
the influence of environment, ordinarily acknowledged as active in modifying forms, to 
gross modification always on the side of deterioration. 
EXPLANATION OF PLATE XVI. 
. Eclophylla alba—norma verticalis. 
. Eetophylla atba—norma lateralis. 
. Ectophylla alba—upper and lower teeth. 
= 
(>) 
mw wm ee 
. Ectophytla alba—lower molar (profile). 
. Ectophylla alba—ramus of lower jaw. 
. Cephalotes peroni—first right upper molar. 
leo) 
=! 
asI OD 
. Cephalotes peroni—first and second right lower molars. 
