3Q 



known geographical range has been extended far to the 

 southward in Mexico. This genus has the further curious 

 history that of the 12 forms recently added 5 of them 

 were described some thirty years ago and had lapsed into 

 synonymy. While many of the species closely resemble 

 each other externally they are easily separated by cranial 

 differences. 



In 1884 Geomys was credited with 5 species, three of 

 which were known only from the United States, and the 

 others, one each respectively, from Mexico and Central 

 America. The recognized United States forms have been 

 increased to 6, and the Mexican and Central American forms 

 to 9, or a total increase of from 5 to 15. l A monographic 

 revision of the genus has been undertaken by Dr. Merriam 

 and is nearly ready for publication, with numerous figures 

 of cranial characters and distribution maps of the species. 



While the increase in our knowledge of the two families 

 Heteromyidse 2 and Geomyidse, or the Pouched Rats and 

 Pocket Gophers, has been so great, it has scarcely been 

 less so in respect to the Muridae. Here the ratio of increase 

 in the number of recognized forms is not only very high, 



Recently described Mexican species are : 



Thomomys orizabtz Merriam, Proc. Biol. Soc. Wash., VIII., p. 14.5, Dec. 

 1893. Mt. Orizaba, Mexico. 



Thomomys peregrinus Merriam, ibid., p. 146. Salazar, State of Mexico. 



1 The present status of the group is as follows, the United States species 

 being : 



Geomys ttiza (Ord). Geomys castanops (Baird). 



Geomys bursariics (Shaw). Geomys personalis True. 

 Geomys bursarius hitescens Merriam. Geomys clarkii Baird. 



The Mexican and Central American species are : 



Geomys mexicanus (Licht.). Geomys scalcps Thomas. 



Geomys gymnurns Merriam. Geomys hisvidus Le Conte. 



Geomys nelsoni Merriam. Geomys cherriei Allen. 



Geomys merriami Thomas. Geomys fumosiis Merriam. 

 Geomys grandis Thomas. 



2 Saccomyidae of Baird, Lilljeborg, Coues, etc. As Saccomys is a synonym 

 of Hetero7nys it becomes untenable as the basis of the family name. Heter- 

 omyidoe is equal to Heteromyinse of Alston, 1876. 



