210 PROCEEDENGS OF THE NATIONAL MUSEUM vol. no 



known North American fossil Plecotus. The geologic age of this 

 species cannot be determined stratigraphically, since the material 

 upon which it is based is from a fissure type deposit. However, the, 

 fauna associated with the bat remains is certainly Pleistocene in age 

 and Gazm (in Gidley and Gazin, 1938, p. 7) concluded from the number 

 of extinct forms present and from the difficulty encountered in identi- 

 fying others as Recent that the Cumberland Cave fauna can hardly 

 be considered Upper Pleistocene, and is more likely Middle Pleistocene 

 in age. There is no reason to suppose that the bat remains were not 

 deposited at the same time as the remainder of the Cumberland Cave 

 fauna. 



P. alleganiensis was similar in many respects to (and possibly 

 directly ancestral to) P. tovmsendii, the Plecotus occurring nearer 

 than any other to Cumberland Cave today. It possessed the primitive 

 characteristics of supraorbital ridge and lack of a sagittal crest. See 

 pages 137-139 for a full description of P. alleganiensis. 



Corynorhinus tetralophodon Handley 



The other American Pleistocene species, C. tetralophodon, from San 

 Josecito Cave, Nuevo Le6n, Mexico, is known from a single skull. It 

 was found in a cave deposit of indeterminable age, but judging from 

 its similarity to Recent forms and from the associated fauna, it is 

 probably Upper Pleistocene (Wisconsin) in age and younger than 

 Plecotus alleganiensis. It differs from Recent forms in possession of 

 a fourth commissure on M^ and in failure of the temporal ridges to 

 coalesce completely. Probably it was related most closely to P. 

 tovmsendii, but possibly was not a direct ancestor of that species. 

 See page 140 for a full description of P. tetralophodon. 



ORIGIN AND DISPERSAL OF EUDERMA AND PLECOTUS 



The paleontological record is so incomplete that a discussion of 

 the origin and dispersal of Euderma and Plecotus necessarily must rely 

 heavily upon speculation. However, with the historical record of 

 other vespertilionid groups in mind, and with the evidence of present 

 day geographic distribution of taxonomic characters in Euderma and 

 Plecotus as a factual foundation, there is ground for speculation on the 

 evolution of these genera. In the systematic section and in the pre- 

 ceding paragraphs of this section the facts have been presented. 

 The remainder of this section is devoted to an interpretation of them. 



Several factors govern the dispersal of bats. Of paramount im- 

 portance are food supply and shelter. For insectivorous forms, such 

 as Euderma and Plecotus, the vegetation controlling the distribution 

 of the bat's insect prey and the climate controlling the distribution 

 of the vegetation are the ultimate critical factors in the bat's dispersal 



