1893. J DR. C. J. rORSYTH MAJOR ON MIOCENE SQUIRRELS. 209 



Tertiaiy Yertebrata : Calamodon^, Anisonchns^, Edocium^, Peripty- 

 cTiKS carinidens^, ditrigonus^, and rliahdodon'^,Palceosjjops Icevideas^, 

 Phenacodus'*, Protogonla°. Secondly, from Lemoiue's 'Etude 

 d'ensemble sur les dents des MammitY'i-es des environs de Reims' ": 

 Hytenodictis^^ , Dissacus^'\ Arctocyon^^, Lopliiodocluerus^*, Plewa- 

 spidotheriuin^\ PaeJiynolojihus maldani^'^, Protodichohane oivenii^^. 

 Thirdly, from Eiitimeyer's ' Eocane Saugethiervvelfc von Eger- 

 kingeu'^^: Ailaravus^^, Pelycodiis helveticus'^°, Hyopsodus'^, '■'■Plesi- 

 adapis ? " ^^, Acotherulum^^, Geboclicerus'\ Lopliiodon parisie)ise'\ 

 Paloplotherium mar/iiam ~'^ ; the last two only so far as their milk- 

 teeth are concerned. 



I ^^ish to answer in advance an objection which will certainly 

 have occurred to the reader. The extreme of complication is met 

 with in such highly specialized recent forms as Hydroclioerus, 

 Phacoclicerus, and Elephas, and to a lesser extent in semi-rooted 

 molars, especially amongst Rodentia. As to the supposed more 

 complex form of these last, it is only apparent. A worn molar 

 of Hystriv, for instance, seems rather more complex than the rooted 

 molar of Erethizon, but on examining unworn grin ding-teeth of 

 Uystrix, even the seemingly very complex milk-tooth only presents 

 five more or less transverse enamel-folds. 



The worn molars show a large quantity of enamel-islets, and 

 thus have a very complex appearance ; but this is not the conse- 

 quence of an augmentation of enamel substance, or additional 

 cusps, but, on the contrary, of diminution of the enamel, which 

 diminishes in the proportion that the \^orn surfaces approach the 

 roots. 



Besides, I have always maintained that in progress of time a 

 new addition may occasionally haA^e occurred in molars ; but it 

 would appear that in one instance at least I M'as mistaken. Con- 

 trary to Owen^^, and all later palaeontologists, with the only 



' ' The Yertebrata of the Tertiary Formations of the West,' pi. xxiv. e. fig. 22. 

 ^ L. c. pi. xxiv. g. fig. 6. 

 ^ L. c. pi. XXV. e. fig. 12. 



* L. c. pi xxiii. d. fig.s. 14, 1.5, pi. xxiv. g. fig. 5. 



* L. c. pi. xxiii. g. fig. 12, pi. xxix. d. fig. 2-4. 

 « L. c. pi. ivi. f. figs. 1 a, 2 a. 



' L. c. pi. 1. fig. 3. 



* L. c. Ivii. b. fig. 1. 



" L. c. pi. XX7. e. fig. 13, pi. xxix. f. fig. 1 «, pi. Ivii. f. fig. 8. 

 '0 L. s. c. 



1' L. c. pi. X. fig. 4. '= L. c. pi. X. fig. 2. 



'••' L. c. pi. X. figs. 14, 18, 20, 22, &c. " L. c. pi. xi. fig. 129. 



1' L. c. pi. xi. fig. 87. '" L. c. pi. xi. figs. 117, 11^. 



'^ L. c. pi. xi. fig. 132. '" L. s. c. 



'" L.c. pi. vii. figs. 18, 19. '^^ L. c. pi. viii. fig. ] (parlim). 



*' L. c. pi. viii. figs. 7, 8. " L. c. pi. viii. figs. Ki, 17, 21. 



" L. c. pi. iv. figs. 22, 24. '■" L. c pi. iv. fig. m. 



=" L. c. pi. i. fig. 8 (f/3 sup.). 2" L. c. y\. i. fig. 1 (d sup.). 



'^'' Rich. Owen, " Description of the Cavern of Bruuiquel and its Organic Con- 

 tents. Part II. Equine remains " (Phil. Trans, vol. 159, London, 1S70, p. 537). 



Proc. Zool. Soc— 1893, No. XIV. 14 



