1893.] DB. C. J. PORSYTH MAJOE ON MIOCENE SQUIRKELS. 187 



systematic Zoology should not take into consideration, more than 

 has been the case hitherto, the chai*acters of the skull and dentition 

 of Sciuromorpha, which characters have been of such excellent 

 service for Myomorpha. 



]My arrangement of the Sciuridse (see the table, p. ISO) contains 

 three subfamilies : — 



1 . Sciurlihv^ including tlje genera of the subfamily Sciurince of 



authors (with the exception of the Elying-Squirrels and 

 some pigmy forms), as well as the members of the sub- 

 family ^Ircfomi/ince (Ci/nomi/>i, Arctoni;/s, SpcnnO]>hilus). 



2. l^teromji'ince, including all the Flying-Squirrels (iSciwoptenis, 



Pteroinijs, /utpetaiirnt^ ). 



3. Nannos^ciuruHf, the Oriental Pigmy Squirrels Sc. e.c'dis, S. 



Miill., 'S'c'. luelanotis, Miill. & Schleg., /SV. conc'mint.^, Thos. \ 

 'SV. wJdMieadi, Thos. ", as well as the Ethiopian Pigmy 

 Squirrel, 'S'c. Dnmiftis, Du Chaillu. 



1 shall say a few words on the Pteronuiitue. when dealing w ith 

 the fossil forms. 



As to my subfamily Sclvfiace,t\xe inclusion]of the ArcfomyitKB in 

 the subfamily Sciuriiuv, which appears at first sight to be a radical 

 change, \^'ill, I am sure, meet with the least opposition. The close 

 relationships of Spermo/thUus to Tamkis and Sciunis are generally 

 recognized ; and my scheme is further justified by the consideration 

 that several Xorth- American species of the heterogeneous genus 

 ^permo[ihihi>> show in their skull and dentition a striking analogy 

 with Xerus, a circumstance which has been generally overlooked. 

 Besides, the dentition of the Arcfomi/ince is so decidedly Sciurine 

 that I do not see why we should any longer keep Arcfo)ii_)/s and 

 SperinopJiUiis artiflcially separated from Xerus and Scinrns, for no 

 other reason than convenience. 



As to the minor divisions, it results from the preceding remarks 

 on the dentition of iSciarum' that the Ethiopian Xcrns occupies, 

 with its three species, a much less isolated position than has 

 hitherto been admitted, inasmuch as numerous species of Ethiopian 

 Squirrels, as ^ell as some Oriental forms, included in the genus 

 Sciunis, have close relations to Xerus in characters, which at the 

 same time approach it to the Hystricomorpha. The cliaracters of 

 the skull of Xerus and its congeners point in the same direction, 

 and consist, to express it briefly, in the elongate form of the 

 craniuin in general and the froutals particularly, coupled with the 

 sliortening of the postorbital processes ; wliereas the renniant of 

 Sciurince ai'e, on the contrary, characteristic for their broad fronlals 

 and the long postorbital processes. Moreover, a small group of 

 Ethiopian Scpiirrels, n-lated to Xerus (Sc. staw/eri, /SV. efil't, Sc. 



' Ann. Mag. N;it. Hist., N(jv. ISsS. pp. 1(17, IdS. /f<ih. Tsabi-lla, B.isilim, 

 Philippines. 



' Ann. Ma','. Nat. Hist. (5) 1887. xx. p. ll.'7; 1'. Z. S. 1889, p. •_>;{!. Jfah. 



