m, 19.7 mm) hairless juvenile; and, finally, one of six females
netted at Santa Rosa on 13 July was pregnant (embryo 23 mm), but the
others evinced no reproductive activity. An adult male, taken at Rivas
with the females mentioned above, had testes that were 6 mm in length.

Bats of the genus _Molossus_ are in need of thorough systematic study.
We think most, if not all, mainland populations of small _Molossus_
with pale-based hairs pertain to the species _Molossus molossus_,
originally described from the Lesser Antilles. Although there is some
variation in size and overall color among our Nicaraguan samples, all
seem to represent that species. Because specimens from Nicaragua
closely resemble examples of _M. m. aztecus_ from Jalisco, Mexico
(Table 3), in external and cranial proportions, we tentatively refer
them to _aztecus_.

In our field experience in both Middle and South America, colonies
of _M. molossus_ tend to be extremely localized, with individual
populations or demes frequently separated by many miles of territory
in which the species seemingly does not regularly occur.

TABLE 3.--Selected measurements of adult _Molossus molossus_.

Table Legend:

Col. A: Number of specimens averaged or catalogue number, and sex
Col. B: Length of forearm
Col. C: Greatest length of skull
Col. D: Condylobasal length
Col. E: Zygomatic breadth
Col. F: Mastoid breadth
Col. G: Breadth of braincase
Col. H: Postorbital constriction
Col. I: Length of maxillary toothrow
Col. J: Breadth across upper molars

======================================================================
A B C D E F G H I J
----------------------------------------------------------------------
Western Jalisco, Mexico

KU 109075, [Male] 38.2 18.0 15.3 11.0 10.5 9.1 3.8 6.2 7.9
KU 109076, [Male] 37.3 17.8 15.3 11.0 10.5 9.2 3.6 6.3 8.1
KU 120540, [Male] 37.7 17.8 15.3 11.0 10.8 8.9 3.9 6.3 8.1
Average 15 ([Female]) 37.1 17.2 14.8 10.7 10.3 8.9 3.8 6.1 7.9
Minimum 36.0 16.5 14.2 10.4 10.1 8.5 3.7 6.0 7.7
Maximum 38.1 17.7 15.2 11.0 10.5 9.2 3.9 6.2 8.2

Departamento de Chinandega, Nicaragua

USNM 337552, [Male] 39.0+- 18.2 15.5 11.0 10.7 9.0 3.7 6.0 8.0
KU 114140, [Female] 37.3 16.8 14.7 10.7 9.9 8.7 3.4 5.9 7.4

3 mi SW Managua, Nicaragua

KU 71009, [Male] 39.8 18.7 16.1 11.1 10.9 8.