744 The American Naturalist. [August, 
heaps of angular fragments of lava, jarred down from the roof by some 
earthquake. Not infrequently two or three superimposed tunnels 
have been united in parts of their length by their respective floors 
having fallen through. In these caves, even on the hottest day, the 
air is fresh and cool, and has a perceptible current down the mountain 
side, which at the constrictions becomes a strong breeze. This cool- 
ness of the atmosphere was a fortunate circumstance for my collecting, 
as because of it I found most of the bats in a state of semi-hibernation, 
enabling me to take with the hand all those within arm’s reach. Prof. 
J. A. Allen’s recently described Vespertilio velifer was the prevailing 
species, abounding in hundreds, and of which I took with the aid of my 
assistant, Sefior Carlos M. Teran, 193 specimens ; 151 being males, and 
the remaining 42 females. This I take to be a fair average of the pro- 
portion of the sexes in what is probably one of their permanent head- 
quarters. P/ecotus macrotis was scattered about in very sparing numbers, 
but five specimens being seen. Unlike my former experience with this 
species in the valley of Mexico, all were found solitary, completely 
isolated from the other species as well as from one another. 
_ While collecting these bats I came across one whose small size 
Immediately distinguished it from the two other species ; yet from its 
general similarity in form, viewed by the uncertain light of a stearine 
candle, and its almost exact identity in color with ve/ifer, led me for 
the moment to suppose that it was a young of that species. But upon 
finding another of these small bats I made a closer examination, and 
at once saw that I had another species to deal with, new to me, and I 
fancied new to science. A search through all the literature of the 
subject that I have at hand confirms me in the belief that it is an unde- 
scribed species. 
Six specimens, five males and one female, were taken, and no 
others were seen. In every case they were hanging from the sides of 
the caves, instead of from the roofs, as was the case with velifer, and 
unlike it were always solitary,—a point on which I place no special 
stress, as I find this and several other habits of bats to vary with 
locality, etc. Some were taken not far from the entrances, where, 
when the eyes were accustomed to the darkness, a faint sort of phos- 
phorescent glow could be seen in the direction of the mouth of the 

cave. Others were taken many hundreds of yards within, where inter- 
vening abrupt angles rendered it absolutely impossible that the slightest 
ray of light could at any time of day penetrate. That this locality is 
not the headquarters of this species I am satisfied ; whether higher up 
in the “erra templada, or below in tierra caliente, will prove to be its 
12 et A NORIO 



