AMERICAN" BATS OF THE GENERA MYOTIS AND PIZONTX 175 



n. THE SPECIES OF MYOTIS OCCTTRRING IN TROPICAL AND SOUTH 



AMERICA 



MYOTIS NIGRICANS (Wied) 



(Synonymy under subspecies) 



Distribution. — From southern Mexico (Chiapas and Yucatan) 

 southward over the warmer parts of South America (including the 

 coastal islands) to Paraguay and southeastern Brazil; islands of 

 Grenada and Dominica in the Lesser Antilles. 



Diagnosis — A small bat not very unlike the North American 

 Myotis calif ornicus in size and general characters, but tail less elon- 

 gated (ratio of tail to head and body in series of specimens averaging 

 about 85), foot relatively larger, the average ratio of its length to 

 that of tibia usually more than 45 and in some races as great as 53 ; 

 ear, when laid forward, extending about to end of muzzle, usually 

 not reaching to nostril but occasionally going beyond it ; metacarpals 

 3 to 5 very slightly graduated, the distal end of the fifth, when folded 

 back, not reaching the elbow by about 2 mm. ; texture of pelage 

 varying from rather short and wooly to long and silky, the longer 

 hairs, when well developed, with glossy tips, these, however, rarely 

 if ever producing a noticeable sheen; color usually dark brown or 

 blackish (rarely grayish or ochraceous), the bases of the hairs not 

 strongly contrasted with the tips; a tawny dichromatic phase rarely 

 present; skull and teeth with no marked peculiarities; forearm 31.6 

 to 39 mm. usually less than 37 mm. ; greatest length of skull ranging 

 from 12.6 to 14.7 mm., usually less than 14.5 mm.; maxillary tooth 

 row 4.7 to 5.6 mm., usually less than 5.5 mm. ; mandibular tooth row 

 5.0 to 6.0 mm., usually less than 5.6 mm.; crowns of upper molars 

 small, m- usually varying from 1.15 to 1.30 by 1.55 to 1.70 mm. 



Ears. — The ear is narrow and delicate (usually 11 to 13 mm. in 

 height from meatus), its anterior border convex to the blunt tip, the 

 posterior border slightly concave below the tip, then convex to the 

 projecting shoulder of the basal two-fifths. When laid forward the 

 tip of the ear reaches about to the end of the muzzle or a little be- 

 3^ond. Tragus about half the height of the ear. with a small basal 

 lobe, marked off by a shallow notch, above which is the broadest part 

 of the tragus. The tip is slightly attenuate and shows a few minute 

 crenulations on the outer edge. 



Wing and membranes. — The wing membrane arises from the side 

 of the foot at the base of the outer toe. Metacarpals 3 to 5 slightly 

 graduated or sometimes the fourth and fifth are about equal and only 

 minutely less than the third. Taking the third finger as 100, the 

 fourth and fifth are respectively as 85 and 78 (59:50.5:46.5 mm.). 

 When the wing is folded the end of the third metacarpal falls short 

 of the elbow by about 2 mm. Practically the entire tail is included 



