100 PROCEEDINGS OF THE NATIONAL MUSEUM 



Figure 2.- — Degrees of development of the secondary cusp in the first upper incisor 



(anterolateral view). 



with an incisor cusp index of lacks the secondary cusp. An index 

 of 1 indicates some development of the secondary cusp, and so on. 



Throughout the text, relative proportions are expressed as per- 

 centages of the greatest length of the skull. 



Color was measured in diffused white fluorescent light, without 

 direct natural light. Capitalized color terms in the text are from 

 Ridgway (1912). There appears to be no sexual dichromatism or 

 seasonal variation in coloration. If such exists, it is so slight that, 

 except in cases of extremely worn pelage, it can be disregarded in 

 comparisons. 



The type of preservation of the specimens examined is indicated 

 in the species accounts by the following abbreviations: a, alcoholic; b, 

 bones (skeleton) ; and s, skin and skull. 



Dental Nomenclature 



The nomenclature of cusps and the numerical designation of teeth, 

 as used in this paper, are outlined|in figure^S. The naming of the 

 individual teeth requires further explanation. 



The complete primitive dentition of adult placental mammals is a 



set of 44 teeth: 



3-3 1-1 4-4 3-3^ 



The nearest approach to this in bats is a set of 38 teeth, lacking one 

 upper incisor and one upper and one lower premolar in each jaw: 



2-2 1-1 3-3 3-3 

 I-3Z3' C iZi' P 3Z3' M 313- 



Incisors: Which of the incisors it is that is always missing in 

 Chiroptera is a matter of controversy. Most authors have believed 

 without much doubt that the consistently missing incisor is the first. 



According to Miller (1907, p. 27) this is indicated, as shown by Winge, by the 

 correspondence of the two upper teeth with the two outer of the lower jaw when 

 the maximum set is present, and also, even more strongly, by the general tendency 

 throughout the group for the premaxillaries to become reduced, particularly 

 along the inner edge. This would inevitably result in eliminating that part of 

 the bone in which the first incisor grows. 



