Ward—The Variations in Proportions in Bats. 641 
a tail of 35 mm. may have only 14 mm. free. Tlie ear shows an 
extraordinary amount of variation in a few individuals; rang¬ 
ing from 12 to 20 mm. in height on heads respectively 20 and 22 
mm. in length. The 12 mm. length is isolated but as the ear 
shows no signs of malformation it is therefore presumable that a 
larger series of specimens would show the connection and also 
straighten up the base of the binomial curve. Between the 
graphs of the head and the ear there is more disagreement than 
agreement in the trend of the lines. Isolated measurements are 
seen by the binomial curves to also occur in the third metacarpal, 
its first phalanx and in the fourth metacarpal, and only misses 
by one of occurring in the fifth. 
A 39 mm. forearm carries an 8 mm. thumb while a fore¬ 
arm 42 mm. has a thumb only 6 mm. in length. Comparing 
the forearms to the second metacarpal we find that the forearm 
usually is the longer with an extreme of 45 :39; in several cases 
they are equal and in two cases the forearm is the shorter, i. e., 
40:41 and 41:42. The second metacarpal is usually shorter 
than the third but may be equal. The first phalanx of the third 
digit frequently exceeds the second but in various cases is equal 
and in three instances, showing no appearance of injury, the sec¬ 
ond phalanx is the longer. Comparing the second to the fourth 
metaearpals we find that they are equal in many cases, that the 
fourth averages larger but that in a few instances this is reversed. 
The fourth metacarpal runs very evenly at from 1 to 3 mm. 
shorter than the third. The disproportion between the first and 
second phalahges of the fourth digit is shown by 12 :8 and 15 :8. 
In his diagnosis of the species in “The Bats of North Amer¬ 
ica,” 1893, Dr. Harrison Allen says: “The first phalanx in the 
third, fourth and fifth digits, exceeds in length the second.” We 
have noted that in the third digit it may be equal to the second 
and in three specimens it is shorter, in one considerably shorter. 
Of the 33 males examined 13 possessed gular sacs but none of 
the 26 females showed this peculiarity which Dobson in his 
monographic catalogue of the Chiroptera in the British Museum 
says is absent in both sexes of the species. 
No. 434, taken at Ixtapalapa in the Valley of Mexico, June 
29th, contained a foetus nearly ready for parturition indicating 
that July is the probable date of birth of this species in that 
region. 
The specimens taken, in March at Tacubaya, about three miles 
4i 
