268 PROCEEDINGS OF THE ACADEMY OF [1894. 



Color. — Upper parts drab-gray, plentifully lined with dusky on 

 median ])art of back and over rump; under parts and feet white; 

 lateral line obsolete ; tail bicolor, brownish above, becoming dusky 

 distally ; white beneath. 



Cranial characters. — Skull similar to C. intermedium obscvriis, but 

 narrower anteriorly (across maxillary arms of zygomata); inter- 

 parietal broader antero- posteriorly ; ascending branches of pre- 

 maxillie reaching posteriorly behind nasals; frontals considerably 

 narrower between orbits. 



ILLUSTRATIONS. 



(Skulls all enlarged li.) 



Fig. 1. Perognathus baileyi, 9 , No. 24,775. Type. Magdalena, 



Sonora, Mexico. 

 Fig. 2. P. columhianus, $ ,'^o.2,d,Ab^. Type. Pasco, Washington. 

 Fig. 3. P. nevadensis, $ , No. 54,565. Halleck, Nevada (type 



locality). 

 Fig. 4. P. longimembris paiiamintimts, S ,1^0. W,H6Q. Type. Pana- 



mint Mts. , Calif 

 Fig. 5. P. fiavus mexicanus, 9, No. 50,713. Tlalpam, Valley of 



Mexico (type locality). 

 Fig. 6. P. (Clurtodipus) nelsoni, 9 , No. 50,214. Type. Hacienda 



La Parada, San Luis Potosi, Mexico. 

 Fig. 7. 1\ (Ch(etodipus) stepheusi, 9 , No. 39,874. N. W. Arm 



Death Valley, Calif, (type locality). 



