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While one of us (Dalquest) was in a dugout canoe that was beingpaddled up a small unnamed tributary of the Rio Coatzacoalcos,through dense jungle, he grasped a decayed and termite damagedtree-trunk projecting approximately three feet above the surface ofthe water to steady the canoe. At that instant two bats were detectedin one of the many small holes in the trunk, which was eightto nine inches in diameter. It was a simple matter to enlarge thehole and extract the animals. Superficially they resembled silvery-hairedbats (Lasionycteris) but their naked interfemoral membranesand other features suggested that they belonged to the genus Myotis.Subsequently, study in the laboratory showed this to be the fact andrevealed also that they are of an heretofore unnamed species whichmay be known as:
Myotis argentatus, new species
Type.—Male, adult, skin with skull, No. 19228, Mus. Nat. Hist., Univ. Kansas;14 kilometers southwest of Coatzocoalcos, 100 feet elevation, Veracruz,Mexico; 2 February 1947; obtained by Walter W. Dalquest; original No. 7052.
Range.—Known only from the type locality.
Diagnosis.—Size medium for the genus (see measurements), tail short; footlong; ears and membranes black; pelage long (maximum length on middle ofback 9 mm.) and black; upper parts with overhairs tipped with whitish especiallyon rump; underparts from posterior part of thorax posteriorly withall of the hairs tipped with this same whitish color; skull with preorbital partsmall in relation to brain case; teeth small in relation to total area of palate;brain case much inflated; ventral margin of foramen magnum evenly rounded.
Comparison.—From Myotis albescens (E. Geffroy) known to us by specimensin the United States National Museum from Paraguay (Tacural), Panama(Tabernilla), and Nicaragua (Prinzapolca R. and Escondido R.), argentatusdiffers in: Body and foot longer; tail relatively shorter (57 and 58% oflength of head and body versus 76 (62-83)% in albescens); tibia shorter;pelage longer, and black instead of brown; silver tipping of fur on hinderback markedly more conspicuous; precranial part of skull, when viewed fromabove, larger in relation to brain case; postorbital constriction less abrupt,that is to say, skull "longer-waisted"; occlusal surfaces of teeth of equal areaand therefore occupying a relatively smaller percentage of total area of palatalsurface; ventral margin of foramen magnum less deeply indented; ventrallyprominent part of basioccipital twice as wide.
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Remarks.—The relatively slight wear on the teeth of the femaleof M BU KİTABI OKUMAK İÇİN ÜYE OLUN VEYA GİRİŞ YAPIN!
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