From _Lasiurus intermedius floridanus_ of the adjacent Floridan mainland, _L. i. insularis_ differs in many of the same ways that it differs from _L. i. intermedius_, except that the differences are even more trenchant because _floridanus_ is smaller than _intermedius_. Indeed, the difference in size between _floridanus_ and _insularis_ is approximately the same as between _Lasiurus borealis_ and _Lasiurus cinereus_. _Measurements._--External measurements (all taken from specimens preserved in alcohol) of the holotype, followed by those of two other females, one from Laguna La Deseada, San Cristobal, Pinar del Rio Province, and the other from Bayate, Guantanamo, Oriente Province, are, respectively: Total length, 164, 161, 150; length of tail-vertebrae, 68, 76, 77; length of hind foot, 12, 12, 13; length of ear from notch, 20, 17, 19; length of forearm, 61.2, 62.6, 61.8. The length of forearm of a study skin from San German (that otherwise lacks external measurements) having wings spread is approximately 55.4. For cranial measurements see Table 1. _Remarks._--Four of the five specimens on which the name _L. i. insularis_ is based differ to such a degree from mainland populations of the species _L. intermedius_ that specific rather than subspecific recognition for the Cuban bat might seem warranted. It is because of the fifth specimen (USNM 254714) that we accord subspecific rank to _insularis_. It is smaller than the other Cuban specimens and except for longer condylocanine length, longer mandibular tooth-rows, narrower interorbital region, and heavier dentition is indistinguishable in measurements from the largest specimens of _L. i. intermedius_ from the mainland. In addition, it appears not to have the enormously developed sagittal crest of the other specimens of _insularis_ although posteriorly the dorsal part of the skull (where the crest is most prominent) is missing. USNM 254714 agrees with the other Cuban specimens in having the mesostyle of M1 and M2 somewhat reduced and in having a small M3 on which the cingulum and second commissure are poorly developed, and this specimen is regarded as representative of the lower size limits of the Cuban population. The skull from San Bias was found in an owl pellet (see de Beaufort, 1934:316). _Records of occurrence._--Specimens examined, 5, all from Cuba, as follows: Pinar del Rio Prov.: Laguna La Deseada, San Cristobal, 1 (Poey Museum). Las Villas Prov.: Cienfuegos, 1 (KU, the holotype). Camaguey Prov.: San Bias, 1 (Amsterdam Zoological Museum). Oriente Prov.: San German, 1 (USNM); Bayate, Guantanamo, 1 (Ramsdem Museum, Univ. Oriente). TABLE 1.--CRANIAL MEASUREMENTS (IN MILLIMETERS) OF THREE SUBSPECIES OF LASIURUS INTERMEDIUS Table Legend: