SOIURID^.— EXTINCT SPECIES. 



931 



with possil)ly one exception,* the remains from tiie Tertiary deposits of the 

 West belong to vviioUy extinct genera. The genera of this family, most abun- 

 dant in the Eocene deposits, and which may l)c nnqiicstionably referred to 

 the Sciuridce, are Paramijs and Scluravus, which are not ajjparcntly very dis- 

 tantly related. The remains referred to these genera indicate species ranging 

 in size from animals smaller than Sciurus hudsonius to those one-fourth larger 

 than Arclomys monax. Other apjiarently Sciurine forms arc the genera Tax- 

 ymys ]\Iarsh, Tilloinys Marsh, Heliscomys Cope, and possibly Colonomys 

 Marsh, and some of the species referred to Gymnoptychus Cope. Gyttino- 

 ptychus chrysodon is said to lack postorbital processes, which at once excludes 

 it from the Sciurida, although the genus has been referred by its author to 

 this familj', togetlier with Ischyromys Leidy.f 



As the majority of tlie extinct species of Sciurida; have l)een described 

 from merely lower-jaw fragments, it is not unlii\cly tliat, if tiiey ever become 

 l)etter known, some of the larger genera, as Paramys, Scluravus, and Gym- 

 7ioj)(ychus, will be found to embrace species not strictly congeneric; it being 

 presumable from analogy that species ranging in size from the size of a large 

 Mouse to that of a large Marmot will hardly prove to be referable to tlie 

 same genera. 



The subjoined account of the extinct forms of Sciuridee is necessarily, 

 from the circumstances of the case, merely a compilation from tiie original 

 authorities. All that is aimed at is to give a connected synopsis of tlic sub- 

 ject, eribracing the leading characteristics of the described forms, with their 

 loc^aties of occurrence, their approximate size, a notice of the data on which 

 our knowledge of them at present rests, and references to the original papers 

 in which they have been described or noticed. Tiiis, owing to the scattered 

 state of the literature of the subject, it has been thought might prove useful 

 to the general student and also to special' "ts. 



SCIURUS CALYCINUS Cope. 



iSoiuni* calyciHHt Cope, Proo. Amer. Phil. 8oc. xil, 1S71, 8G. 



Described from "two imperfect rami of the lower jaw, with the incisor 

 and first, second, and third inferior molars in situ", found in the Port Ken- 



* Professor Cope refers one species from Colorado, described first as a Paramyn, to Sciurus, remark- 

 iug that the remains thns referred do " not differ in any degree from corresponding parts of tlie existing 

 Squirrels".— (^nn- Sep. V. S. Geo}. Sun. Terr, for 1S?3 (1874), p. 475.) 



t Ibid. p. 474. 



