_Remarks._--The long-nosed bats from San Josecito Cave do not differ appreciably from _Leptonycteris nivalis longala_ Stains, the largest Recent subspecies of the species, and the subspecies that occurs in the same geographic area today. Average and extremes of three cranial measurements of 22 specimens from San Josecito Cave, followed in parentheses by the average and extreme measurements of 23 adult _L. n. longala_ from the type locality, 12 mi. S and 2 mi. E Arteaga, 7500 ft., Coahuila (after Stains, 1957: 356), are: Greatest length of skull, 28.2, 27.2-28.9 (27.5, 26.1-29.0); least interorbital constriction, 5.0, 4.8-5.4 (4.8, 4.1-5.4); breadth of braincase, 11.1, 10.6-11.6 (10.7, 10.1-11.2). The San Josecito specimens average larger than the series of Recent specimens in all of these measurements, especially breadth of braincase, but there is considerable overlap in each case and the extremes of greatest length of skull and of least interorbital constriction do not exceed the extremes in the Recent series. _Desmodus stocki_, new species _Holotype._--Cranium, lacking post-incisor dentition on the left side, zygomatic arches and auditory bullae; Los Angeles County Museum (CIT) No. 3129; from Pleistocene deposits of San Josecito Cave, near Aramberri, Nuevo León, México. _Referred material._--Twelve additional partial crania, LACM (CIT) 2946-50, 3127-30, 3940-41, 2 unnumbered. _Diagnosis._--Resembling the Recent _Desmodus rotundus_ but differing from it as follows: Skull larger (see measurements and Figs. 1-2), heavier and more massive; rostrum and braincase relatively as well as actually broader, interorbital region relatively more constricted; braincase more rounded (less elongate) as viewed from above; nasals less concave in lateral view; narial vacuity broader in relation to greatest length of skull, more nearly heart-shaped; palate broad, less concave medially; mesopterygoid fossa relatively and actually broader anteriorly, the sides nearly parallel; zygomatic arches (judging from No. 2950, the only specimen with a complete arch, the left) less rounded in outline, appearing broader owing to the more constricted interorbital region. Dentition larger and heavier than that in _rotundus_, but otherwise differing only slightly from it; upper incisor less concave on cutting surface (see Figs. 3-4); premolar and molar slightly less bladelike, with heavier roots.