AMERICAN BATS OF THE GENERA MYOTIS AND PIZONYX 137 



its greatest length 12.2 to 15.0 mm. 5 maxillary tooth row ranging 

 from 4.5 to 6 mm. ; lower tooth row (excluding incisors) 4.9 to 6 mm. 

 Ears low and bluntly rounded, barely reaching the nostril when laid 

 forward. Foot decidedly less than one-half the length of tibia, the 

 ratio of its length to that of tibia about 41 ; calcar distinctly keeled. 

 Fur on the under side of wing membrane extending out to the level 

 of the elbow. 



Ears. — The ear is short, barely reaching the nostril when laid 

 forward, its anterior margin strongly convex, its upper half beveled 

 abruptly backward to the broadly rounded tip. Tragus short, about 

 half the height of ear from meatus (5 : 10 mm.) ; at its base a small 

 rounded lobe, above which the anterior and posterior margins con- 

 tinue nearly parallel half way to the tip whence the posterior out- 

 line is sharply beveled forward to the tip. 



'Wing and Tnemhranes. — The wing membranes arise from the base 

 of the toes. Third metacarpal longest; second, fourth, and fifth 

 about equal, or the two latter graduated so that 4 is shorter than 3, 

 and 5 is shorter than 4. When folded the third metacarpal falls 1 

 to 1.5 mm. short of the elbow. Taking the third finger as 100, the 

 fourth is 83, the fifth 77 (66 : 55 : 51 mm. ; specimen from Menlo 

 Park, Calif.). Tail involved in membrane except at its extreme tip, 

 where the terminal vertebra alone projects. Free border of uropa- 

 tagium without fringing hairs. 



Foot. — The foot is delicately formed, its length decidedly less than 

 half the length of the tibia (ratio of foot to tibia in 2 specimens 

 from Lower California 40.8; in 10 specimens from Nicasio, Calif,, 

 41.7; in 10 from localities within the area inhabited by the interior 

 race, 40.7). Calcaneum about as long as the free edge of the uropa- 

 tagium, ending in a distinct but minute lobule. At about the length 

 of the tarsus from the ankle, a low elongate keel arises. 



Fur. — Pelage full and long, about 7 mm. on lower back. Above, 

 the hair extends out on to the interfemoral membrane over an area 

 approximately the length of the femur. Below, the wing membrane 

 is usually well furred as far out as a line joining the elbow and the 

 knee. Membranes blackish brown. 



Skull. — The skull is of characteristic form, small and delicate with 

 the rostrum shortened and the profile of the brain case elevated 

 abruptly, giving a '' pug-nosed " effect (pi. 1, p. 7, fig. 10). Occiput 

 high and slightly inflated. Temporal ridges slightly developed but 

 usually traceable with a lens. They unite to form a low sagittal crest 

 anterior to the occiput. Posterior to this point of union they bow 

 outward, to continue back with a rather characteristic outline, cut- 

 ting off a somewhat triangular area whose sides are convex instead of 

 58518—28 10 



