The peculiar shape of the incisor of _stocki_ is shared to some extent with Diaemus youngi, a Recent South American desmodontid. However, _stocki_ does not otherwise resemble _D. youngi_, differing from it as follows: Skull larger and heavier; interorbital constriction much narrower; zygomatic arches less strongly bowed; skull less compact, more elongate; braincase and rostrum relatively much narrower in relation to greatest length of skull. Furthermore, specimens of stocki show no trace of the minute M2 attributed to _youngi_ by de la Torre (Proc. Biol. Soc. Washington, 69: 191, 1956). For cranial measurements of _youngi_ see Sanborn (Jour. Mamm., 30: 283, 1949). [Illustration: FIGS. 1-4. Fig. 1. Dorsal view of holotype of _Desmodus stocki_, × 1-1/2. Fig. 2. Dorsal view of _Desmodus rotundus murinus_, male, KU 54969, La Mula, 13 mi. N Jaumave, Tamaulipas, × 1-1/2. Fig. 3. Lateral view of left upper incisor of _D. stocki_, LACM (CIT) 2950, × 2-1/2. Fig. 4. Lateral view of left upper incisor of _D. r. murinus_, female, KU 54967, La Mula, 13 mi. N Jaumave, Tamaulipas, × 2-1/2.] _Remarks._--The essential differences between _D. stocki_ and _D. rotundus_ are in size and proportion. I do not doubt that the two species are closely related; possibly _stocki_ is ancestral to _rotundus_. The species is named in honor of the late Professor Chester Stock, under whose direction the fossil materials from San Josecito Cave were obtained, and who, at the time of his death, was studying the mammalian fauna from the cave. _Eptesicus cf. grandis_ (Brown) _Referred material._--One rostrum, with P4-M3 on the right side and P4 only on the left, LACM (CIT) 2990. _Remarks._--This specimen is referred provisionally to _E. grandis_. The dentition is larger and heavier, and the ridges and depressions on the dorsal surface of the rostrum are more pronounced than in Recent _E. fuscus_. The P4-M3 length is 6.1 (approximately 6.1 in the holotype of _grandis_, less in _fuscus_); least interorbital constriction, 4.2 (4.3 in the holotype of _grandis_, more in _fuscus_); breadth of rostrum between infraorbital canals, 6.4; breadth across P4, 7.3. TABLE 1.--Cranial measurements of two species of _Desmodus_.