Claws flat and small: anterior extremities with a distinct thumb: mammae pectoral: penis free and pendulous.
Incisors varying in number; summits of the grinders armed with sharp points: anterior and posterior extremities connected by a naked expansion of the skin, adapted to flight: fingers very long.
Incisors two above and four below: grinders five on each side above and below: nostrils with two foliaceous appendages, the posterior one erect: ears free; tragus wanting.
Incisors four above and six below: grinders varying in number: nostrils without foliaceous appendages: ears sometimes free, sometimes united at their base; tragus always present.
(1. Vespertilio). Ears moderately large, lateral, separate: grinders from four to six above, and from three to six below on each side.
(2. Plecotus). Ears very large, much longer than the head, with their inner edges united at the base above the eyes: grinders five above and six below on each side.
(3. Barbastellus). Ears moderate, united at the base above the eyes: a flat naked space on the forehead surrounded by a membraneous edge: grinders four on each side above and below.
§ ii. Incisor, canine, and molar teeth not all present, or not forming a continuous series.