mm 



SACCOMYID^— PltELIMlNARY CONSIDEUATIONS. 



489 



each should rank as a family; for, as I iiavc already attempted to show,* 

 the great diiference in configuration between the Ge.omyid(e ixnA Saccomyida, 

 liiough only a matter of secondary consequence, is coordinated with struc- 

 tural characters important enough to warrant the erection of the sublamily 

 Saccomijince into a family Saccomyi.da, distinct from, though unquestionably 

 standing next to, the family GeomyklcB. 



It may be conceded that this valuation was virtually, if onl} incidenlally, 

 set forth in 1868 by Dr. J. E. Gray,t who, though using a terminology ("iSVvc- 

 comyina:") indicative of a subfamily, nevertiieless speaks of "the family" of 

 Pouclied Mice, from which Geomys and Thoinomys are excluded. 



In 1872, Dr. T. Gill J first formally recirded a family SaccomyidcB as 

 equivalent to the subfamily SaccomijincE of Baird, 1857, and of Gray, 1868, and 

 to the subsequent //e^erowi^i«<£ of Alston, 1876. The group tiius accorded 

 full family rank was placed nexl to the family Geomyida, the two together 

 constituting one of the author's numerous taxonomic refinements, a "super- 

 family" (or series) Saccomyoidea, which was hence exactly equivalent to the 

 group Saccomyina as founded by Waterhouse and the family Succomyidce as 

 endorsed by Baird. Such term, Saccomyouka, may be accepted as an expres- 

 sion of the unquestionable fact that the Saccomyixta and the Geomyidm are 

 more intimately related to each other than they are to any other family of the 

 Rodents. 



Thus following Professor Gill in determining a family Saccomyida so 

 drawn as to exclude Geomyida, I wish, before giving my characterization of 

 the group, to note what disposition has been made of its component genera 

 by several authors. Dr. LeConte, in 1853,§ and Professor Baird, in 1857, || 

 b(jth treited only of North American forms, recognizing but two genera, 

 Dipodomys and Perognathus (-f subg. Cricetodipus). Dr. Gill made no sub- 

 division of the family. Mr. A'ston recognized three genera, — Dipodo>nys, 

 Peiognatlius and Heteromys. Di. "'••ay, and, following him, Hr. Peters,** 

 divided the Pocket Mice into two gro. p of no assigned value, namely, 



* Uulletiu U. 8. Oeol. aud Geogr. Surv. Terr. 3d Ber. No. % J^b, pf 83 ttq. ; and Proo. Acad. PhiU. 

 1875, p|). 873 ttq. 



t Synopsis of the Species of RaccoiuyiniD, or Pouched Mice, in the Collection of the British Museum. 

 < Proc. ZoOI. Soo. Lond. 16(>8, pp. 199-306. 



t ArrauKeuient of the Families of Mammals. With Analytical Tublos. Prepared for the Smithsonian 

 Institution. < Smiths. Misc. Cull. No. 330. (Svo, Washington, 1873.) 



i Ueniaiks on the Meuns Dipoihiiiiys and Perognathus. < Pmc. Pliilti. Acad, vi, 1853, pp. 334, 335 



y Mammals of North America, p|i. 4(F>-43<i. 1857. 

 ** Muoatsb. kOiiigl. prunss. Akud. WiHseusch. Ucrliu, Mai 1874, p. 355. 



