, peglike, and
displaced lingually; M3 much reduced, area of its crown less than
a third that of M1.

Members of this genus are notable for having three and even four
young (more than other bats). In North America at least _L.
borealis_ and _L. cinereus_, are migratory.

Provisional Key to the Recent Species of _Lasiurus_

1. Color reddish or grayish (not yellowish); normally two premolars on
each side of upper jaw.

2. Occurring on Antillean islands (color reddish).

3. Length of upper tooth-row less than 4.5 mm. (occurring on
Hispaniola and Bahamas) _L. minor_.

3'. Length of upper tooth-row more than 4.5 mm. (not occurring
on Hispaniola and Bahamas).

4. Greatest length of skull less than 13.9 mm. (occurring
on Cuba) _L. pfeifferi._

4'. Greatest length of skull more than 13.9 mm. (occurring
on Jamaica) _L. degelidus._

2'. Occurring on mainland and coastal islands of North and South
America; also on Galapagos and Hawaiian islands (color reddish or
grayish).

5. Total length more than 120 mm.; color grayish _L.
cinereus._

5'. Total length less than 120 mm.; color reddish.

6. Upper parts brick red to rusty red, frequently washed with
white; lacrimal ridge present.

7. Not occurring on Galapagos Islands _L. borealis._

7'. Known only from Galapagos Islands (both ear of 7.6 mm.
and thumb of 6.4 mm. allegedly shorter than in _L. borealis_
of adjacent mainland; presence of lacrimal ridge not verified)
_L. brachyotis._

6'. Upper parts not brick red to rusty red; lacrimal ridge not
developed.

8. Forearm more than 46.5 mm. (48 in only known specimen,
a male); dorsum bright rufous (absence of lacrimal ridge
not verified) _L. egregius._

8'. Forearm less than 46.5 mm.; dorsum not bright rufous.

9. Upper parts mahogany brown washed with white;
forearm less than 43 mm _L. seminolus._

9'. Upper parts deep chestnut; forearm more than 43 mm.
(44.8 in only known specimen, a female) _L. castaneus._

1'. Color yellowish; only one premolar on each side of upper jaw.

10. Total length more than 119 mm.; length of upper tooth-row 6.0
mm. or more _L