1022 MB. OIDPIELD THOMAS ON THE [DeC. 15, 



100. Tachyoryctes, Eiipp.' 



[CJirysomys, Gray, List Mamm. B. M. 

 p. 150 (1843).] 



! B. SpaIiAoin^. 



'■ ■ 101. Sjmlax, Giild. 



, Nov. Comm. Petroji. xiv. art. i. p. 409 



(1770). 



VIILGeomyidas. 



i ' .102. Geomijs", Raf. 



Am. Month. Mag. ii. p. 45 (1817). 

 ■ • -' 103. Thomomys, Wied. 



N. Act. Leop. xix. pt. i. p. 383 (1839). 



IX. Heteromyidse. 



A. DlPODOMYIN^. 



104. Dipodomys, Gray. 



Ann. Mag. N. H. vii. p. 521 (1841). 

 ' ' 105. Perodipus, Fitz. 



SB. Ak. Wien, Ivi. p. 126 (1867). 



106. Microdipodops, Merr. 



N.Am. Faun. no. 5, p, 115 (1891). 



B. Hetebomtin^e. 



107. Pero(pia{hus^,W\eA. 



N. Act. Ac. Leopold, xix. pt. i. p. 369 

 (1839). 



108. Heteromys, Desm. 



Mamm. ii. p. 313 (1822). 



nervice to me. Some important observations on the relations of the BhicO' 

 myinm to Ihe Masearono Signioclontca are given by Dr. Forsytli Major, sui^rh 

 p. 079. 



' Tlie African Bamboo-Rats, given provisionally the above name by Eiippell, 

 were rightly distinguished by Gray, but the distinction has been generally lost 

 sight of till now. The molars are of quite a different structure in the two 

 groups. 



It is unfortunate that Eiippell's name has to be used for this genus, as he 

 deliberately rejected the idea of its being distinct (from Bathycrgns'.), and yet 

 proposed the name in case other workers thought it valid. It is to be hoped 

 that there are few people now loft who would do a thing like this, by which au 

 author attempts to secure priority for his own name at the expense of somebody 

 else's work, while he fears to take the responsibility of describing a new form 

 for himself. Some naturalists even refuse to accept such names, and I wish I 

 could feel justified in doing the same. 



2 Dr. Merriam has divided the old genus Geomys into eight genera, but for 

 the purposes of the present paper these may be most conveniently treated as of 

 subgeneric rather than generic rank, sound us their basis as natural groups no 

 doubt is, 



^ Dr. Coues (Mon. N. Am. Eod. p. 495, 1877) speaks of separate subfamilies 

 for I'erogimthus and lldcromys; but they seem really lo be very closely allied 

 to each other, especially if some of the larger species of the former, such as 

 ■IK 'paradoxus, be compared with members of the 11. allciti group of IJctennnys. 



