Iy93.] DR. C. J. FOltSYTK MAJOlt oy .MIOC'ENK SQCIIUIELS. 19o 



iuferior in number to the nou-flviug Sciuromovpha, unci have, to all 

 appearances, greally diminished from Tertiary times up to the 

 present, so that their special means of locomotion do not seem to 

 ha\e pr()^'ed of more value in the struggle for existence to those 

 of the non-Hying. 



(o) One may thirdly suppose that there is no direct connexion 

 whatever between the Sc'mrojiteri and recent tSciuri or Sciurlda'. 

 From Tertiary times up to the present, the species of Mying- 

 iSquirrels have been gradually diminishing in number, their 

 characters having proved inadaptive, whilst the species of Sciuridai 

 have been increasing. The points of similarity in the grinding- 

 teeth of Sciuras prevosti and ^f:iarOj>kr as Jiinhrlatas, on the whole, 

 are very slight (and so are those between Sciaropterus volueella 

 and Sciurus hudsonius) ; with a little practice it is at once possible 

 to distinguish an isolated tooth of tlie one fi'om that of the 

 other. Tlieir skulls, nioreo\'er, are very different. 



For my part, I rather incline towards the third supposition, 

 although admitting that the grounds on A^hich it is based may 

 not be convincing. At any rate, the characters of the cranium as 

 well as those of the dentition, though greatly A'arying, give on the 

 whole a family likeness to all tlie riying-Squirrels, so that I cannot 

 but separate theui into a chstinct subfamily fi'om the Sciui'ina;. 



The Pteroini/s, soisu sfrtctissinto, have probably evolved from a 

 single >Sci>.iro/ite)'i(s-\ike form, and Eupetaunis is apparently the 

 more specialized descendant of some Pteromys. 



The really important characters in which some Sciuri and 

 SpermofihiH approach the Sclwopteri, as in the restricted 

 iuterorbital region of Colohotis, the general elongation of the 

 frontals of Aarious Scinridje, the general shape of the grinding- 

 teeth in Eusciurus, and in the stronger development of the first 

 ridge in the upper molars of the Otos/iermo/JiUl, are all such that 

 they may be considered as ancient inheritances. 



Therefore we Jieed not aduiit any recent connexion between the 

 Scu(r<ijj(cri and the above-mentioned members of .Sciuritlae. 



Anatomical characters and palteontological evidence pohit in the 

 same direction, viz. that the Sciarojitcri are the little modified 

 remnants of a very old and ouce widely spi-ead group. There is 

 not sulHcient evidence for admitting that they have evolved From 

 forms of non-flying Squirrels identical with, or very closely allied 

 to, those actually living ; their power of %iug luay not be a com- 

 paratively recent character. They are specialized, no doubt, 

 compared to the remnant of Sciuridjo ; but the ancestral non-Hying 

 types may neither have been ISciuridtc nor even JSciuromorpha. 



It would be more consistent with these views to jdace the Flyiiig- 

 Squirrels in a distinct family; but for this it will be time enough 

 when their recent as well as their fossil forms are better known 

 than is the case at ])resent'. 



' Tliu present paper was comiiluU'ly liiiislicd wlioii I (ir»l bcfairic partiiilly 

 acquainted with H. Winge'a " Jorcif undue og luilovondo Gnnvore (Rodentiu) 



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