'''i89o!"'] PROCEEDINGS OF THE NATIONAL MUSEUM. 295 



tiou of the wings iu flight. One of tUe most interesting measurements 

 is that of the width of the third digital interspace. This space, so 

 small in Fteropidw, Molossi, and in Noctillo, is wide in Fhyllostoniidw, 

 excepting Phyllostoma. Another interesting feature is the extent of 

 the incision on the free margin of the interfemoral membrane. In well- 

 preserved specimens of G. brevicauda the incision is conspicuous, while 

 in the type of C. castanea, which is also iu good condition, the incision 

 is absent. Yet in slightly macerated specimens of C. brevicauda the 

 incision disappears, showing that it is a character which is dependent 

 upon tonicity and not on any distinctive structural peculiarities, and 

 can not, therefore, have much value. One of the marked ranges of 

 measurements is seen in the length of the tail. The shortest tail is 5™™. 

 long and the longest 7'"'". The tip of the tail answered iu three speci- 

 mens to the middle of the femur, iu four to the junction of the middle 

 with the lower third, and in two the tail lacked one-fifth only in being 

 as long as the femur. In none, therefore, was the tail as long as in the 

 single example of C. castanea. 



The length of the thigh varies from 12 to 15™™. Hence the relative 

 lengths of these quantities will be alsovariable, especially so since even 

 in the same individual the length of the tail does not tautogenize* with 

 the leugth of the femur. The length of the tibia — a character of value 

 in Cheiroptera — varies from 14 to 18'"™. The length of the fore-arm, 

 perhaps the most important single measurement which can be taken, 

 varies from 35 to 40™™. 



The following includes the variations of the manus and their range: 



The length of the head appears to be subject to very slight variation, 

 namely, from 22 to 23™™. That of the ear, from 12 to 13i™™, a slight dif- 

 ference, and yet one which might disturb the novice in attempting to 

 identify the species, since the proportion between the height of the ear 

 and the length of the muzzle is so often used in descriptions of bats. 



*Tautogeneity— a word introduced by Professor Eolleston as a more correct term 

 in this connection than correhition. 



t Au apparent auoii-.aly exists ou the left side of specimen No. 3993. There are two 

 phalanges to the second digit. 



