Merriditi — Little Kuoiru Kaixjdmn Rats. 145 



Skiill. — Rather long and narrow ; sides of fronto-parietal shield approxi- 

 mating anteriorly; maxillary arches cojnpressed. Compared with pana- 

 mlnliuus and agilis the maxillary arches are much less spreading, their 

 outer margins slope more strongly backward, and the frontals are narrower 

 between lachrymals (more wedgeshape). 



Measarcituntx. — Type sjiecimen (female): Total length, 275; tail verte- 

 brae, 162 ; hind foot, 42. Average of 8 from type locality: Total length, 

 282; tail vertebrae, 171 ; hind foot, 42.3. 



Perodipus microps sp. nov. 



Ti/pe from Lone Pine, Owens Valley, Inyo Co., California. Adult male, 

 No. lift 1, U. S. National Museum, Biological Survey Collection. Decem- 

 ber 22, 1890. E. W. Nelson. Original No. 138. 



Cliaracters. — Size small, as in ordi and rolurnljidiins ; ears small and pale; 

 color pale buflFy ochraceous, much paler than ordi and columbianus. 



Skidl. — Small and rather narrow, and very different from that of any 

 known species ; compared with ordi and columbianus, braincase narrower; 

 nasals narrower; premaxiila? broader; parietals (together) much more 

 acutely pointed posteriorly ; breadth of single parietal much less than 

 length (in ordi length and breadth subequal) , maxillary arch much weaker 

 and more slender, without external angle ; supraoccipital between bullae 

 narrower ; incisors thinner (anteroposteriorly) and more vertical (less in- 

 curved). 



Measurements. — Type specimen: Total length, 282; tail vertebrae, 165; 

 hind foot, 41. Average of 5 from type locality: Total length, 270; tail 

 vertebrae, 158 ; hind foot, 40.6. 



Perodipus microps levipes subsp. nov. 



Ti/pe from Perognathus Flat, Emigrant Gap, Panamint Mountains, Cali- 

 ifornia (altitude 5200 ft.) Adult male, No. IHH. U. S. National Museum, 

 Biological Survey Collection. April 16, 1891. Vernon Bailey. Original 

 No. 2668. 



Characters. — Size small, little larger than microps from Lone Pine; ears 

 small ; color pale buffy ochraceous, as in ynicrops. Skull small, with large 

 posteriorly bulging bullae, and narrow, weak maxillary arches. Compared 

 with microps the hind foot and skull as a whole are larger ; bullae decidedly 

 larger ; parietals less acutely pointed posteriorly. From F. cabezon,v, which 

 has equally large bullae, it may be told at a glance by the small, narrow, 

 weak, and tapering maxillary arches, and by the very much smaller ears. 



Measurements. — Type specimen: Total length, 288; tail vertebrae, 156; 

 hind foot, 43. Average of 10 : Total length, 289.5 ; tail vertebrte, 164 ; hind 

 foot, 42.4. Total length of skull 38, contrasted with 35 for microps. 



