AMEEICAN BATS OP THE GENERA MYOTIS AND PIZONYX 189 

 MYOTIS CHILOENSIS (Waterhouse) 



(Synonymy under subspecies) 



Distribution. — South America from northern Ecuador to southern 

 Chile ; eastward to the coast of Argentina. 



Diagnosis, — Like Myotis niffncans but larger (forearm 35 to 43.4 

 mm., usually more than 37 mm.) ; greatest length of skull 14.2 to 16.2 

 mm., usually more than 14.5; maxillary tooth row 5.4 to 6.3 mm,, 

 usually more than 5.5 mm. ; mandibular tooth row 5.5 to 6.5 mm., 

 usually more than 5.8 mm.; ear longer, extending distinctly be- 

 yond tip of muzzle when laid forward; and crown area of upper 

 molars obviously greater {m? usually 1.30 to 1.50 by 1.70 to 2.00 

 mm. instead of 1.15 to 1.30 by 1.55 to 1,70 mm.), see Plate 1, Figure 

 2 (p. 7). 



Exterrud characters. — The general external characters do not differ 

 appreciably from those of Myotis nigricans except that the entire 

 animal is larger and more heavily built, the foot is more robust and 

 the ear is longer, usually 14 to 15 mm. This last feature is especially 

 well developed in one of the local forms occurring in the Andean 

 region. 



Fur and color. — The fur tends to be longer and more silky than 

 in Myotis nigricans (longest hairs at middle of back about 8 mm.), 

 and in some of the races the glossy tips to the hairs on the dorsal 

 surface are more conspcuous, though not sufficiently abundant to 

 produce a definite sheen like that which occurs in M. albescens. The 

 general color ranges from a rich, dark brown to light grayish or 

 yellowish. 



Skull and teeth. — Except for their greater size the skull and teeth 

 do not show any special peculiarities as compared with those of 

 Myotis nigricans. Brain case smooth, with at most a slightly 

 developed sagittal crest, 



Remarhs. — The differences between Myotis chiloensls and M. 

 nigricans are not very obvious at first sight, but the two animals 

 appear to be perfectly distinct from each other. In collections 

 Myotis nigricans is the commoner of the two, and the material ex- 

 amined appears to show that it has the wider geographical range. 

 The grayish and yellowish forms of Myotis chiloensls are at once 

 distinguishable from M. nigricans by their color alone, no corre- 

 sponding phases of the smaller animal having yet been discovered. 

 The same is true of the largest race ; it obviously exceeds all known 

 forms of M. nigricans in size. True M. chiloensls and a dark form 

 rather widely distributed in the central Andean region are less 

 easily recognized, as their size and general color are not verj^ differ- 

 ent from those of the better known species. The longer ears and 



