| on anterointernal | on anterointernal | face | face --------------------+-------------------------+----------------------- P1 (occlusal view) | Less than a seventh as | More than a seventh | large as canine | as large as canine --------------------+-------------------------+----------------------- P1 (labial view) | Concealed by C1 and P4 | Not concealed --------------------+-------------------------+----------------------- P4 | Touching canine | Not touching canine --------------------+-------------------------+----------------------- i3 | Touching i2 and c1 | Separated by space | | from i2 and c1 --------------------+-------------------------+----------------------- p3 | Lower than anterior | As high as anterior | cusp of canine | cusp of canine --------------------+-------------------------+----------------------- Distance from c1 | Less than length of m2; | More than length of to m1 | premolars crowded | m2; premolars less | | crowded --------------------+-------------------------+----------------------- +Pipistrellus hesperus+ (Synonomy under subspecies) _Range._--Arid Sonoran life-zones of western North America from Washington southward to Jalisco. _Characters._--Smoke Gray to Buff Brown (Capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) dorsally; total length, 60 to 86; foot less than half as long as tibia; tragus blunt with terminal part bent forward; skull nearly straight in dorsal profile; inner upper incisor unicuspidate; outer upper incisor with accessory cusp on anterointernal face; P1, viewed from occlusal face, less than a seventh of area of canine, and from labial aspect concealed by canine and fourth premolar; lower, third premolar lower than anterior cusp of canine; lower premolars crowded, distance between canine and first molar less than length of second lower molar. _Remarks._--In the United States and in the northern part of Mexico, _P. hesperus_ is the smallest bat found. Little is known about its habits. It emerges earlier in the evening than other species of bats. The frequency with which it is seen near cliffs suggests that it finds concealment under rocks. In winter, in Nevada (Hall, Mammals of Nevada, p. 150, 1946), _P. hesperus_ has been found singly in crevices in the roofs of mine tunnels.