1919J Dixmi: Bushy-tailed Wood Rats of Calif orm-a 57 



FOSSIL FOEMS 



A supposedly extinct species of bushy-tailed wood rat, Teonoma 

 spelaea, Sinclair (1905, p. 148) has been described from Potter Creek 

 Cave, Shasta Comity, California. The type of this fossil species is the 

 ''anterior two-thirds of a skull of an adiilt individual in which the 

 teeth are not much reduced by wear. ' ' The main points of difference 

 claimed for spelaea are: "the rostrum and incisive foramina are 

 decidedly shorter [than in cinerea], . . . the premaxillae extend farther 

 back beyond the nasals, the nasals taper more posteriorly, and the 

 frontals have a greater interorbital width." In the fossil form the 

 enamel loops of the molar teeth of the lower jaw are supposed to be 

 more evenly balanced on the two sides of the axis of the tooth row than 

 in cinerea. 



The type skull of spelaea was examined by Kellogg (1912) and 

 compared with additional fossil specimens from Potter Creek and 

 Samwel caves as also with specimens of Recent Neotoma c. occidentalis, 

 this being the form existing today in the Shasta region. In the course 

 of this study it was discovered that in the type of the fossil form the 

 incisive foramina and the rostrum were actually longer than were 

 those of three young adult females of N. c. occidentalis in the Museum 

 of Vertebrate Zoology. ' ' The extension of the premaxillae is less than 

 that of one of the specimens with which it is compared, and greater 

 than that of the other two, showing that this is a variable character. 

 •. . . The main points in which the fossil fomi differed from N. c. occi- 

 dentalis were in longer upper tooth row and larger teeth. ... In regard 

 to the enamel loops of the lower molars being more evenly balanced 

 in the fossils, no difference between them and those of N. c. occidentalis 

 could be found and the writer has placed all the specimens from both 

 caves under this living species" (Kellogg, 1912, pp. 159, 160). 



The present author has examined the type specimen of "Teonoma 

 spelaea," and careful measurements substantiate Kellogg 's findings. 

 Furthermore, a skull of N. c. occidentalis now at hand is found to have 

 as heavy dentition as that of the type of spelaea. The length of the 

 upper tooth row of this specimen (no. 11151) is 10.5 mm. as compared 

 with 10.2 mm. in the type of spelaen. In the light of this additional 

 evidence it seems best to consider the fossil specimen which was made 

 the basis for the name spelaea as inseparable from N. c. occidentalis. 



DISTEIBUTION 



It will be seen from the accompanying map (fig. C) that bushj'- 

 tailed wood rats are restricted to the higher mountains in the eastern 

 and northern parts of the state. Although existing on such isolated 

 ranges as tlie White and Panamint mountains, in the Inyo region, 

 they are not known to occur on any of the high mountains in southern 

 California and are unknown from any point in the state west of the 

 Sierra Nevada and south of San Francisco Bay. 



