34 BULLETIN" 144, UNITED STATES NATIONAL MUSEUM 



KEY TO THE AMERICAN SPECIES AND SUBSPECIES OF MYOTIS AND PIZONYX 



Foot greatly enlarged, its length about equal to that of tibia or skull, the 

 digits and claws conspicuously compressed ; wing membrane abruptly nar- 

 rowed at level of knee ; a glandular mass in membrane between forearm and 

 fifth digit; second premolar, both above and below, larger than first. 



Pizonyx (p. 33). 



Size large, exceeding that of any known American species of Myotis; 



forearm 60 mm. or more; greatest length of skull about 22 mm. (Gulf 



of Californiu) P. vivesi (p. 209). 



Foot not greatly enlarged, its length decidedly less than that of tibia or 

 skull; the digits and claws not conspicuously compressed; wing membrane 

 not narrowed at level of knee ; no glandular mass in membrane between fore- 

 arm and fifth digit ; second premolar, both above and below, smaller than 

 first [size in the known American species medium or small ; forearm not 

 known to attain a length of 60 mm.] Myotis (p. 30). 



Species Occukking in Tropical and South America 



Wing from tibia and sides of back -close to the median line ("Uruguay" but 



probably not American) M. pilosus (p. 208). 



Wing from foot and sides of body. 



Breadth of rostrum across canines equal to or greater than interorbital 



constriction; wing attached at ankle M. simus (p. 205). 



Breadth of rostrum across canines less than interorbital constriction ; wing 

 attached at base of outer toe. 

 Maxillary cheek teeth unusually small relatively to area of palate; skull 

 with rostrum shortened and brain case enlarged and rounded. 



M. albescens (p. 200). 

 Maxillary cheek teeth not unusually small relatively to area of palate; 

 skull with normal rostrum and brain case. 

 A well developed sagittal crest always present in adults ; color usually 



reddish M. ruber (p. 197). 



A well developed sagittal crest rarely present in adults ; color seldom 

 reddish. 

 Skull small, its greatest length usually ranging from 13 to 14.5; teeth 

 small, the crown of m' usually less than 1.25 by 1.70 mm. ; ear 

 usually not extending beyond nostril when laid forward. 



M. nigricans (p. 175). 

 Greatest length of skull usually more than 14 mm. ; foot usually less 



than half as long as tibia M. n. nigricans (p. 177). 



Greatest length of skull never as much as 14 mm. ; foot usually more 

 than half as long as tibia. 

 Skull extremely small ; forehead rising with unusual abruptness. 



M. n. dominicensis (p. 183). 

 Skull not extremely small ; forehead rising normally. 

 Color probably averaging darker (.southern Mexico). 



M. n. extremus (p. 181). 

 Color probably averaging lighter (Island of Curagao). 



M. n. nesopolus (p, 182). 

 Skull large, its greatest length usually ranging from 14 to 16 mm. ; 

 teeth large, the crown of w' usually more than 1.30 by 1.70 mm. ; 

 ear always extending beyond nostril when laid forward. 



M. chiloensls (p. 189). 



