G2 ]\Ii-. K. Aiitlerseii on (he Bats of tJie 



a sea, which, liowovcr, probably was subdivided into a 

 northern and southern portion, comuiunieating by a compa- 

 ratively naiTow sound between tiie Central Brazilian and 

 Bolivian highlands. The bed of the nurthera part of tins 

 ancient sea forms, appro timately , the geographical line of 

 separation between the two races of M. megalotis : broadly 

 speaking, we find south, south-east, and east of that line 

 (Brazil, Guiana, ^'enezuela) M. m. typica ; west and north- 

 west of the ancient sea-hed (Colombia, through Central 

 America to Mexi(;o) M. m. rnexicana. — Later on, the passage 

 from the Centi'al Brazilian highlands must liave been easy to 

 Bolivia and Peru, likewise from Venezuela some distance 

 north-westwards (and to coast-islands, as Trinidad and 

 Tobago). That on other points, too, some shifting of the 

 areas in the course of time has takju place is only what was 

 to be expected. It is, no douljt, in a comparatively late 

 period that the species has spread through Central America 

 to Mexico. 



M. minida. — M. minuta is very closely related to M. meya- 

 lotis ; the complete resemblance in the skulls, in the ears 

 and nose-leaves, the strong development of tiie ear-band, and 

 the presence of a frontal groove in both species tend to show- 

 that their common origin cannot lie very far back. But in 

 the strong reduction of p^ and p^ M. minuta has reached a 

 higher stage than any other species of the genus. The more 

 complicated ear-band (prot)ably making the ears more inde- 

 pendent of each other in their movements) and the shortening 

 of the tail are also evidences of a higher specialization. 



M. hirsuta. — So far as the premolars arc concerned, 

 M. hirsu/a is practically on the same level as J/, mega/utis 

 (though there is, perhaps, a slightly more pronounced 

 tendency to reduction oip^). But the inner upper incisors 

 (i'j are much less compressed antero-posteriorl}', tlius 

 without that approximation to chisel-shape so evident in the 

 other species ; the skull is less vaulted ; and the band 

 between the ears very low. Its origin from the Mirro- 

 nycteris stem may, therefore, be assumed to date back to a 

 time when these three peculiarities were not carried so far as 

 in the now living M. megalotis. 



GItjpJionycteris. — Some of the peculiarities which entitle 

 Gli/jj/tonijctcris to the rank of a distinct genus arc already 

 foreshadowed in Micronycteris. In M. megalotis and minuta 

 the cutting-blades of the upper inner incisors (r) are 

 conspicuously compressed in antero-posterior direction ; in 

 Glyphonycteris this feature is carried to an extreme. lu 

 M. minula the principal cusp of p"^ is situated very near the 



