AMEKICAN BATS OF THE GENERA MYOTIS AND PIZONYX 63 



Ears. — The ears are of moderate length; when laid forward they 

 reach to the nostril (alcoholic specimens). When the ear is held 

 erect, the lower third of its external border forms a strongly jutting 

 shoulder, above which the margin is very slightly convex, then very 

 slightly concave to the bluntly rounded tip. The result is that the 

 upper two-thirds of the ear conch appears to be narrowed and with 

 a nearly straight posterior margin. In Myotis ludfugus the basal 

 shoulder is much less pronounced and the conch itself is wider so 

 that the outer edge is more nearly straight from base to tip, the upper 

 part of the ear is not so narrowed, and its general appearance is less 

 scimitar-shaped. 



The tragus differs from that of Myotis ludfugus in the size and 

 form of the basal lobe; this lobe is larger in proportion and nearly 

 semicircular in outline; the tragus is about one-half the height of 

 the ear from meatus (7:13.5 mm.). The anterior edge is nearly 

 straight, the posterior slightly convex above the base, then tapering 

 in the upper third to the bluntly rounded tip. The upper third of 

 the posterior edge is often slightly crenulate. 



Wing and Tneyiibranes. — The Aving membrane arises from the tarsus 

 just proximal to the bases of the toes. The metacarpals are distinctly 

 graduated, the third longest, the fourth slightly shorter, the fifth 

 again shorter (about 2 mm. less than the third). When folded, the 

 third metacarpal falls from 1 to 2 mm. short of the elbow (as com- 

 pared with 2-5 mm. in M. luoifugus) . Taking the third fmger as 100, 

 the fourth is 85, the fifth 79 (56:48:44.5 mm.). The first phalanx 

 of the fourth finger is about 1 mm. shorter than the second (8:9 mm.) ; 

 but in the fifth finger the opposite relation obtains, for the first is a 

 very little longer than the second (7.5 : 7) , or they are practically equal 

 (7.5:7.5). The minute terminal vertebra of the tail is the only one 

 free from the membrane. Under a lens may be seen numerous short 

 stiff hairs springing in several rows from close along the free edge 

 of the interfemoral membrane ; they do not, however, form a fringe. 



Foot. — The foot is proportionally stout and long, the ratio of its 

 length to that of tibia ranging from about 50 to about 54. The inner- 

 most toe is slightly but evidently shorter than the others, the tip of 

 its claw reaching only a little beyond the base of the claw of digit 2. 

 The long calcar extends three-fifths of the distance from the heel to 

 the tail, and ends in a minute lobule. It is quite without projecting 

 keel. 



Fur. — The pelage is full and of medium length, the hairs about 

 5 mm. long on the lower back, bicolored ; dark bases are evident every- 

 where except on the lower abdomen. The fur extends out on to the 

 interfemoral membrane slightly beyond a line joining the knees, 

 above and below. Underneath, the wings are thinly haired nearly 



