County Museum (CIT) No. 3129; from Pleistocene deposits of
San Josecito Cave, near Aramberri, Nuevo Leon, Mexico.

_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.

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_, x 1-1/2. Fig. 2. Dorsal view of _Desmodus rotundus murinus_,
male, KU 54969, La Mula, 13 mi. N Jaumave, Tamaulipas, x 1-1/2. Fig. 3.
Lateral view of left upper incisor of _D. stocki_, LACM (CIT) 2950, x
2-1/2. Fig. 4. Lateral view of left upper incisor of _D. r. murinus_,
female, KU 54967, La Mula, 13 mi.