In each of our two specimens there is no sagittal crest but instead a low ridge one millimeter wide which marks the space between the margins of the two temporal muscles. Allusion already has been made to the resemblance of the newly named _Myotis argentatus_ to the silvery-haired bat, _Lasionycteris noctivagans_ (LeConte). The whitish tips of the hairs are slightly more yellowish in _argentatus_ but the difference is so slight as to be detected by only the most careful comparison. The remainder of the pelage in _argentatus_ is black as in the darkest individuals of _Lasionycteris_. Among named kinds of the genus _Myotis_, the species _argentatus_ most closely resembles _Myotis albescens_ which, up to now has been recorded from as far south as Argentina, in South America, and as far north as Nicaragua, in Central America (Miller and Allen, Bull. U. S. Nat. Mus., 144:202, 203, 1928). The differences detected between the two species are indicated above in the paragraph of comparisons and some other differences can be detected by comparing measurements given below with those of _M. albescens_ as recorded by Miller and Allen (_op. cit._: 204-205). In initial comparisons with _albescens_, only Paraguayan specimens were employed. It was felt that specimens of _albescens_ from the northernmost localities of occurrence might more closely resemble _argentatus_. Accordingly, we appealed a second time to Dr. A. R. Kellogg for comparative material and he lent us the specimens (alcoholics with skulls separate) in the U. S. National Museum from Central America. These also differ from our newly named bat in the same fashion as do the South American specimens. Further, the number and magnitude of the differences between _albescens_ and _argentatus_ greatly exceed any that can be pointed to between the American subspecies of any other one full species of the genus _Myotis_. Full specific, rather than mere subspecific, status, therefore, is suggested for the bat here named _Myotis argentatus_. _Measurements._--The adult, male type, and the immature female specimen measure, respectively, as follows: Head and body, 55, 51 mm.; tail, 32, 29; tibia, 13.7, 13.2; foot, 8, 9; forearm, 33.0, 34.5; thumb, 5.8, 5.7; third metacarpal, 32.2, 30.5; fifth metacarpal, 31.5, 30.3; greatest length of skull, 14.5, 14.0; condylobasal length, 13.8, 13.0; zygomatic breadth, 9.1, 9.0; interorbital constriction, 4.3, 4.0; breadth of brain case, 7.5, 7.4; occipital depth, 5.7, 5.7; mandible, 10.5, 10.0; maxillary tooth row, 5.3, 5.0; maxillary breadth at M3, 5.5, 5.7; mandibular tooth row, 5.6, 5.3. _Specimens examined._--Two, from the type locality. _Transmitted October 20, 1947._ FOOTNOTE [1] Assistance with field work is acknowledged from the University of Kansas Endowment Association.