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PROCEEDINGS OF THE NATIONAL MUSEUM. 



297 



seeu tbatia three only of C, hrevicauda (the males, Nos. 3230, 3229, 4L92 — 

 and thus suggestive of sexual distinction) is the difference between the 

 widths of the second and third spaces less than 10™'", while in the single 

 example of 0. castanea (also a male) the difference amounts to but 9'""\ 



In this connection I may allude to the value which attaches to the 

 last named measurements in the study of the Cheiroptera. 



If a specimen of a bat, which is preserved in spirit, is so held in the 

 hand that the wing is supported in the position of flight, it will be seen 

 that the intervals between the metacarpal bones hold a definite relation 

 to each other. 



The width of the spaces between the metacarpals, now being recorded 

 (the measurements are taken at their widest parts), it will be seen that 

 the second interspace is the narrowest and the fourth the widest. In 

 this way a formula may be stated. It is proper to add the length of 

 the forearm to the formula, since this measurement is one of relative 

 constancy and is of importance in framing the diagnosis of the species. 



Examination of the table herewith presented exhibits at a glance the 

 marked contrasts which obtain in the Phyllostomidw in the composition 

 of this formula. 



It is especially interesting to note the diflerence which exists between 

 the widths of the second and third interspaces. It will be observed that 

 no two formuliTe are alike, nor is any fixed ratio preserved between the 

 formulfB of genera which are allied. Nevertheless the measurements 

 are sufficiently distinctive to warrant the recommendation that they be 

 taken in all discriminating studies, not only of the Phyllostomidce, but 

 of the entire order. 



Fonnulw of Ihe widths of second, Ihird, and fourth intcrsjyaces in the (jenera of Phyllo- 



stomidw. 



Lopbostoma , 



Schizostonia , 



Macrotus 



Desniodus 



Vampyrops 



>Sturniia 



ChiloDycteris 



Oarollia 



Vanipy I us 



Loncboglossa 



Mouophyllus 



A rtibeus 



Bracbypbylla 



Morinoopa 



Phyllostoma 



Tbe following includes the forninlie in families other 

 than tbe Phyllostomidaj: 



Rhyncbon'y cteris 



Cynopterus marginatus 



Vespertilio muiinua 



Epomophorus franqueti 



Rbinopoma 



Atalapha 



Molossus rufus 



Noctilio 



Pteropus edwardsii 



Diflference 



between 



III and IV. 



5 

 7 

 10 

 10 

 10 

 12 

 9-12 

 12 

 12 

 14 

 18 

 18 

 19 

 45 



