186 DE. c. J. roRSTin majob on miocette sQriBBELS. [Feb. 28, 



of Elefiaria (E. mollis, xpeciosa, and cocdtiea), as well as of some 

 Jdnds of beetles and all sorts of caterpillars. A very similar 

 food will in all likeliliood hereafter prove to be preferred by 

 <SV. hosei^. 



The molars of the semi-hypsodont Pferomi/s (Plates YIII. and 

 IX. fig. 19) bear the same relation to those of Scinropterus as the 

 molars of the Xems-ty^e do to those of the Sciunis-vulr/ans-type. 

 In both, the valleys appear deepened and narro\\ed, but in Pteromiis 

 the narrowing is effected by the \erlical increase of the \Arinkles 

 referred to in Sciuropfenis molars (Plates YIII. and IX. figs. 20, 

 21, Plate IX. figs. 2, 5), — the result of which is that the cup of an 

 inferior molar is filled up by these ramifications of the enamel, and 

 the crov\n of both upper and lower molars becomes almost plane. 

 The Eocene Ailnravus from Egerkingen (Switzerland) % which I 

 consider to be a Eodent, is in this respect somewhat intermediate 

 between Pteromj/s and Schtroptenis. 



I have called the A'cz-ns-type of molar a somewhat specialized 

 one, and am justified in doing so, .as the teeth presenting it are 

 no more brachydout — brachydontism being the ]>rimitive con- 

 dition. The brachydout crown of Sciuromoi-pha is at the same 

 time bunodont ; whereas the semi-hj psodont teeth are more or 

 less, and the hypsodont teeth are completely, lophodont. 



Another small group of Ethiopian Sqiurrels — Sc. stangeri (Plates 

 YIII. and IX. fig. 7), 'SV. ehii, and Sc. anhmnii (Plates YIII. and 

 IX. fig. 8) — deserves the name of brachydout Xeri, as it shows from 

 what form of brachydout molar the Yi?;v(s-type may have origi- 

 nated. Other charactei's of this same small group to be mentioned 

 presently hkewise point towards the Ilystricomorpha, not^^ith- 

 standing their perfect brachydontism. 



In concluding these general remarks on the form of the Sciurine 

 molar, I repeat what has already been stated, \'iz., that in perfectly 

 brachydout Sciurine teeth the cusps tend towards a longitudinal 

 arrangement — two marginal series in the lower molars : t\\ o 

 marginal and one or more, more or less complete, intermediate 

 series in the upper molars. This circumstance is of importance, 

 as pointing towards the primitive arrangement of the molar cusps, 

 and we shall have to revert to it when treating of the original 

 type of molar. 



III. liemarls on the Classification of the ScirBiD.T:. 



We have now to consider some of the bearings of the foregoing 

 remarks on Sciurine molars on Classification. 



Classification was not my original purpose ; but some of the 

 results arrived at seem to me of some intei-e.st in this respect too, 

 so that I think they may be worth mentioning. Xor do I see why 



^ Mr. Hose informs me that Sc. ho.m is a groimcl-squirrel like Sc. insignis ; 

 this fact goes far to streugtlien tlie supposition tliat the food of both is similar. 

 - L. Riitimeyer, /. o. pi. vii. figs. 18, 19. 



