1893.J DB. C. J. FORSYTH MAJOR Olf MIOCEKE SQUIRRELS. 209 



Tertiary Vertebrata : Calamodon'^, Anisonchus^, Edomtm^, Peripty- 

 chus carinidens*, ditrijonus', and rhahdodon'^,Paheosijops Icevidens'', 

 Phenacodus", Protogonia^ . Secondly, from Lemoine's 'Etude 

 d'ensemble sur les dents des Mammifures des en\drous de Eeims' ^° : 

 ffycenodictis", Dissacus^^, Arctocyon'^^, Lophiodoclioerus^*, Pleura- 

 spidotherium'^'% Pachynolopihus maldaiii^'^, Protodichobune oive^iii". 

 Thirdly, from Eiitimeyer's ' Eociiue Siiugethierwelt von Eger- 

 kingen'^'': Ailuravus^"', Pehjcodus helveticus'"', Hyopsodus'^, ''Plesi- 

 ad(qns?"'^, AcotJieridum-^,'^ CebocJioems'^\ Lophiodon parisicnse^\ 

 Paloplotherium mag mini '^^ ; the last two only so far as their milk- 

 teeth are concerned. 



I ^A-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 Hydrochoerus, 

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

 molars, especially amongst Eodentia. As to the supposed more 

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

 of Hi/strir, for instance, seems rather more complex than the rooted 

 molar of Erethizon, but on examining unworn grinding-teeth of 

 Eystriv, 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 worn surfaces approach the 

 roots. 



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

 new addition may occasionally have occurred in molars ; but it 

 would appear that in one instance at least I was mistaken. Con- 

 trary to Owen", and all later paleontologists, with the only 



' ' The Vertebrata 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. figs. 14, 15, pi. xxiv. g. fig. 6. 



^ 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. pl. XXV. e. fig. 13, pi. xxix. f. fig. 1 a, pi. Ivii. f. fig. 8. 

 '0 L. s. c. 



1' L. c. pl. X. fig. 4. 1' L. c. pl. X. fig. 2. 



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



1' L. c. pl. xi. fig. 87. ^^ L. c. pl. xi. figs. 117, 118. 



" L. c. pl. xi. fig. 132. " L. s. c. 



" L. c. pl. vii. figs. 18, 19. ^° L. c. pl. viii. fig. 1 (partim). 



" L. c. pl. viii. figs. 7, 8. =^ L. c. pl. viii. figs. 16, 17, 21. 



=' L. c. pl. iv. figs. 22, 24. ^ L. c. pl. iv. fig. 30. 



^' L. c. pl. i. fig. 8 {d^ sup.). '"' L. c. pl. i. fig. 1 {d sup.). 



^^ Eioh. Owen, " Description of the Cavern of Bruniqueland its Organic Con- 

 tents. Part II. Equine remains " (Phil. Trans, vol. 159, London, 1870, p. 537). 



Proc. Zool. Soc— 1893, No. XIY. 14 



