AMERICAN BATS OF THE GENERA MYOTIS AND PIZONYX 201 



Type locality. — Paraguay. 



Type specimen. — None specified. Geoffrey's name is based on the 

 " chauve-souris douzieme " of Azara/^ hence the type locality is con- 

 sidered to be Paraguay, perhaps near Asuncion where Azara resided. 



Distribution. — Warmer parts of America from Costa Rica to 

 Venezuela, Paraguay, and Patagonia. Limits of range imperfectly 

 known. 



Diagnosis. — Externally much like Myotis chiloeTisis except that 

 the foot is slightly larger (average ratio of foot to tibia about 52 

 instead of about 48 or less), the ear is shorter and the tips to the 

 longer hairs of the posterior half of back, in fresh pelage, usually 

 form a noticeable pale area. Skull with brain case inflated and 

 rostrum relatively short and weak. , Cheek teeth much smaller than 

 those of Myotis cMloensis (the crown of m^ usually 1.20 to 1.25 by 

 1.35 to 1.50), and smaller relatively to the area of the palate than 

 in M. cMloensis or any other known American member of the genus. 



Ears. — The ear is small, narrow and thin; its tip not markedly 

 narrowed, the anterior outline slightly but evenly convex, the pos- 

 terior outline not noticeably concave below the tip but nearly straight 

 and gradually passing into the convex outer base without making a 

 sharply defined shoulder. Tragus narrow and of nearly the same 

 width throughout, tapering slightly at the tip, its total height less 

 than half the total height from anterior lower margin to tip of ear 

 (about 5.5:12.5 mm.). Laid forward the tip of the ear reaches the 

 nostril. 



Winff and membranes. — Wing from the side of the foot at the base 

 of the toes. The metacarpals are slightly and evenly graduated, the 

 third longest (in an average specimen as 32:31.5:31). The fingers 

 are graduated in the same order. Taking the third finger as 100, the 

 fourth and fifth are respectively as 87 and 81 (58.5:51:47.5 mm.). 

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

 elbow by about 2 mm. The fur extends thinly on the under side 

 of the wing as far as a line joining the knee and the proximal third 

 of the humerus. On the interfemoral membrane above it extends 

 only a short distance, about to a line joining the knees. The terminal 

 vertebra of the tail is obviously free. 



Foot. — The foot is large, both absolutely and proportionally to the 

 length of tibia. Its length is slightly more than half that of the 

 tibia (average ratio in 7 specimens from Paraguay, 52.5). The 

 calcar is long (about 16 mm.) and exceeds the free border of the 

 interfemoral membrane by about 4 mm. It is usually without a 

 well-defined keel and terminates in a minute projecting lobule. 



1' Essals sur rhlst. nat. des quadrupfedes du Paraguay, vol. 2, p. 294, 1801. 

 58518—28 14 



