HETEROMYIDJ^: 173 



Length about 220 mm. (8.65 inches) ; tail vertebrae 125 

 (4.90) ; hind foot 27 (1.05) ; ear from crown 11 (.43). 



Type locaHty, Dulzura, San Diego County, California. 



The Dark Pocket-Mouse has a somewhat limited range, as 

 far as is now known. This is the foothills and mountains of 

 San Diego County and the adjoining part of northern Lower Cali- 

 fornia. I believe it will ultimately prove to be a subspecies of 

 califonikiis. In the lower part of its range P^fognathus fallax 

 also occurs, and they may be trapped in the same spot. As they 

 are very much alike the novice is likely to consider themi both 

 of the same species, but a little examination of the ears v\iill show 

 a difiference; falla^x has a short round ear while feiiioralis has a 

 longer and pointed ear. 



Perognathus spinatus Merriam. (Bearing spines.) 



SPINY POCKET-MOUSE. 



Above grayish buff mixed with dark brown; below white; 

 lateral line obsolete; tail drab gray above, white below; spines 

 large and extending forward on the sides, sometimes to the 

 shoulders, the rump spines partly brown, the others white ; skull 

 rather flat ; rostrum- broad ; mastoids small. 



Length about 182 mm. (8.10 inches); tail vertebrae no 

 (4.33) ; hind foot 21.5 (.85) ; ear from crown 6 (.24). 



Type locality, 25 miles below Needles, California. 



Spiny Pocket-Mice frequent the arid hills around the Colo- 

 rado Desert and in the southeastern part of the Mojave Desert, 

 east to the Colorado- River, which they do- not appear to cross. 

 They are replaced on the east bank of the Colorado- by the less 

 spiny intermedkis. Spiny Pocket-Mice are most plentiful along 

 the western side of the Colorado Desert and southward into- Low- 

 er California, but they are not plentiful anywhere. They do not 

 seem to care for the open Desert or for wide valleys, but like the 

 bottoms of rocky slopes where they can come into narrow sandy 

 gulches. I have several times seen them running about among 

 the rocks at twilight in summer, and they may be more crepuscu- 

 lar than other species. 



