18<i DK. r. J. roRSTTiT ^lAJOR OS MIOCENE SQmBBELS. [Eeb. 28, 



of Eletlaria (E. mollis, .t/h'ciosa, and coccinea), as well as of some 

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

 food will in all likelihood hereafter prove to be preferred by 

 Sc. hoseV. 



The molars of the semi-hypsodont Pteromifs (Plates VIII. and 

 IX. fig. 19) bear the same relation to those of Sehn'opierus as the 

 molars of the AVr»^?-type do to those of tlie SiluniH-vtih/mis-type. 

 In both, the valleys appear deepened and narrowed, but in Ptcromys 

 the narrowing is effected by the vertical increase of the wrinkles 

 referred to in Schin.ptenis molars (Pkites VJlf. and IX. figs. 20, 

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

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

 the crown of both upper and lower molars becomes almost plane. 

 The Eocene Aihinn'iis from Egerkingen (Switzerland) ", which I 

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

 between Ffcromi/s and Sc'mroj items-. 



I have called the Xen(s-ty\)e of molar a somewhat specialized 

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

 no more brachydont — brachydontism being the primitive con- 

 dition. The brachydont crown of Sciuromorpha is at the same 

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

 less, and the hypsodout teeth are completely, lo])hodont. 



Another small group of Ethiopian Squirrels — Sc. siangeH (Plates 

 YIII. and IX. fig. 7), *SV. ehil, and Sc. avhtnmi (Plates YIII. and 

 IX. fig. S) — deserves the name of brachydont Xcri, as it shows from 

 what form of brachydont molar the X^'r^rs-type may have origi- 

 nated. Other characters of this same small group to be mentioned 

 presently likewise point towards the Hystricomorpha, 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, viz., that iii perfectly 

 brachydont .Sciurine teeth the cusps tend towards a longitudinal 

 arrangement — two marginal series in the lower molars : t wo 

 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. 



11 r. lieiDarl's on the Classification of the ScirBiD.T:. 



We have now to cousider 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 interest in this x*espect too, 

 so that 1 think they may be worth uientioning. Nor do I see why 



' Mr. Hose informs ine {\xi\i Sc. hosei is a ground-squirrel like Sc. insignis', 

 this fact goes far to strengthen tlie supposition that the food of both is similar. 

 - L. Eiitimeyer, /. c. pi. vii. figs. 18, 19, 



