140 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iio 



Mexican PleistoceneTspecies, P. tetralophodon, appears to be more 

 remote. 



Specimens examined: Four cranial fragments and 27 fragments of 

 mandibles from Cumberland Cave, Md. 



Plecotus tetralophodon Handley 



Corynorhinus tetralophodon Handley, 1955b, p. 48. 



Holotype: CIT (Vert. Paleont.) 192/2989; well preserved skull 

 with worn teeth (lacking mandibles, auditory bullae, hamular proc- 

 esses, all incisors, right canine, and the minute premolar, P^, from 

 each maxilla); collected by Chester Stock in Pleistocene deposits of 

 San Josecito Cave, near the town of Aramberri, southern Nuevo 

 Ledn, Mexico, elevation 7,400 feet. 



Distribution: Known only from the Pleistocene fauna of San 

 Josecito Cave, Nuevo Le6n, Mexico (fig. 14). 



Description: Similar to Recent species of the subgenus Coryno- 

 rhinus in most cranial details. Anterior nares relatively small and 

 rounded in outline (dorsal view); brain case relatively shallow; supra- 

 orbital ridges lacking; temporal ridges prominent and converging 

 posteriorly, so that they meet but do not completely merge; inter- 

 maxillary notch relatively small; extension of palate posterior to M^ 

 relatively short; median postpalatal process styliform; basial pits 

 deep and well defined. Tooth rows crowded; teeth relatively fragile 

 (not robust) ; canine with small internal cingular cusp ; anterointernal 

 cingular cusp of P* only slightly indicated; M^ with well developed 

 fourth commissure, almost equaling third commissure in length. 



Measurements: Holotype, in millimeters: Greatest length, 15.6; 

 zygomatic breadth, 8.2; interorbital breadth, 3.4; brain case breadth, 

 7.7; brain case depth, 5.3; maxillary tooth row, 5.0; postpalatal 

 length, 5.9; palatal breadth, 5.7. 



Comparisons: A well developed fourth commissure of M^ distin- 

 guishes P. tetralophodon from related species. This commissure is 

 barely indicated in other New World species of Plecotus and in 

 Euderma maculatum ; there is no trace of it in the Old World Plecotus 

 auritus, in which even the third commissure of M^ is reduced. 



The degree of shallowness in the cranium of P. tetralophodon (brain 

 case depth equals 34 percent of greatest length) is rarely equaled in 

 Recent specimens of the subgenus Corynorhinus. It is observed in 

 less degree in Euderma maculatum, Plecotus auritus, P. phyllotis, and 

 possibly in P. alleganiensis. 



Absence of a sagittal crest is a character shared with Euderma 

 maculatum, Plecotus alleganiensis, and P. phyllotis. The temporal 

 ridges usually are even farther apart in those forms, however. A few 

 specimens of P. mexicanus and P. townsendii resemble P. tetralophodon 

 in this respect. 



