158 [September, 



^ Much of the confasion in the species has arisen from a laudable desire to iden- 

 tify and retain the names of the older authors, even when unsupported by suffi- 

 cient descriptions. Science has now, however, advanced so far, that it is time to 

 get rid of all hypothetical synonyms by excluding definitely all that is too im- 

 perfect for use, even when sanctioned by great age or character. I have accord- 

 ingly placed at the end of this paper, references to all such descriptions as seem 

 to be unfit for quotations under any individual species, and would recommend 

 that these having now been collected together, should be hereafter passed over 

 in respectful silence. 



The synonyms of this genus are as follows :Geomys Raf. (1817): 

 [DiPLoSTOMA Raf. (1817); Sacchophorus Kuhl^ (1820); Ascomys Lichtenstein, 

 (1822); PsEUDOSTOMA Say^ (1823); Oryctomys, Eydoux, (1827); Thomomys 

 Wied. (1839). 



The two last names belong only to the second division of the genus, or those 

 with smooth incisors, that character having been assumed as of generic value. 



The following analytical table expresses the relation between all the species 

 which I have had an opportunity of examining. Four species of Richardson be- 

 longing to group B. and G. castanops, the place of which is uncertain, have not 

 been included, as I have not seen them, and can only take what has been writ- 

 tea by others upon them. 



A. Dentes primores superiores profunde sulcati. 

 a. Cauda-fere nuda. 



1. Rufo-fuscus fere hispidus G. hispidus Lee. 



2. Supra rufus : primores superiores bicaniculati G. canadensis Lee. 

 :i. Supra plumbeus : primores superiores unisulcati G. pineti^a/. 



b. Cauda pilosa. 



4. Supra nigricans, primores superiores unisulcati G. mexicanus Rich. 



5. Supra fuscescens, primores superiores bicanaliculati G. oregonensis Lee. 



B. Dentes primores non sulcati. 



6. Supra rufescens, infra albicans, auribus brevibus G. rufescens Lee. 



A. Dentibus primoribus sulco profundo exaratis. 



a. Cauda fere nuda. 



1. G. hispidus, pilis concoloribus rufo-fuscis minus subtilibus tectus, cauda 

 brevi nuda, auribus obsoletis. 



Length from nose to root of tail, ----- 11-5 



Tail, ,-- 3 



Anterior foot to end of claw of third toe, - - - i7 



Posterior foot to end of claw of third toe, - - - 1.9 



One specimen, Mexico, Mr. Pease's collection. This species differs from all 

 the others in having the fur very coarse and harsh, and entirely of a reddish 

 brown color. Beneath it is slightly grayish, but the difference in color is by no 

 means obvious. The ears are not at all prominent, being merely openings in the 

 skin. The whiskers are as long as the head. The upper incisors are broken off, 

 but enough remains to show that they were deeply grooved near the middle of 

 the anterior surface ; it is impossible to determine if there is a second submar- 

 ginal groove. The tail is completely naked except at the root. The feet are 

 precisely as in the other species of this division of the genus. 



2. G. c an ad ens i s, supra rufus, infra flavicans, pilis subtilibus, basi satu- 

 rate plumbeis, genis pedibusque albidis, cauda mediocri nuda, auribus brevibus, 

 primoribus superioribus bisulcatis. 



Length from nose to foot of tail, - - - - - 6-7 



" Tail, 3-2 



Anterior foot to end of third claw, - - - - 1-3 



Posterior foot to end of third claw, - - , - 1-3 



