Warren — Dichromatism in Neotoma mexicana fallax. 37 



in my collection from various Colorado localities my attention 

 was attracted by certain differences in color. Colorado Springs 

 is the point nearest the type locality (Cold Hill, Boulder 

 County, Colorado) from which I have specimens. My speci- 

 mens agree very well with ( roldman's description in his revision 

 of the genus,* which was made from the type and topotypes, 

 having a creamy huff on sides and hack. Specimens from 

 Howard, Fremont County, and Salida, Chaffee County, are very 

 similar. Not one of some ten skins has any indication of a 

 buff pectoral hand. 



The San Acacio skins differ from these in having ochraceous 

 hull' instead of cream buff, and I found this to he the case with 

 skin.- from Grand Junction, and Sieber Ranch (mi Little 

 Dolores Creek), Mesa County; Bedrock and Coventry, Montrose 

 County; Cortez and Ashbaugh's Ranch, Montezuma County. 

 One skin from Coventry has a light huffy wash on the belly. 

 All of these southwestern Colorado rats are a more distinct buff 

 above than the Colorado Springs and Salida animals. Win 

 some of these skins are spring and summer specimens, others 

 were taken at fall and winter dates which make them abso- 

 lutely comparable with those from the more northeastern locali- 

 ties, which happen to have been taken at that season. A few 

 of the southwestern animals show a pectoral hand. 



Goldman, op.cit., mentions cases of dichromatism in various 

 species of Neotoma, including N. fallax from Copperton, Mount 

 Taylor, and Grant, New Mexico, though judging from Ins 

 description none, with possiblj' one exception from Grant, 

 seem to be of as strongly marked a character as that which I 

 have just described. Other species in which he found dichro- 

 matism are Neotoma albigula from New Mexico, N. torquata 

 from south-central Mexico, A', desertorum from ("tab localities, 

 and possibly .V. lepida stephensi from near Grant, New Mexico. 



The plates herewith illustrate the difference between the two 

 phases, Plate I showing the dorsal surface, and Plate II the 

 ventral. Figure 1 in each case is the melanistic example, and 

 Figure 2 the normal. 



e 



*N. A. Fauna No. 31, Revision of the Wood Rats of the Genus Neotoma. By E. A. 

 Goldman, ran. 



