| OCR Text |
Show 1893.J DR. C. J. FORSYTH MAJOR ON MIOOENE SQUIRRELS. 209 Tertiary Vertebrata: Calamodon1, Anisonchus2, Ectocium3, Peripty-chus carinidens4, ditrigonus5, and rhabdodone,Pala>osgops leevidens7, Phenacodus8, Protogoniaa. Secondly, from Lemoine's 'Etude d'ensemble sur les dents des Mammiferes des environs de Reims'10: ffycenodictis11, Bissacus12, Arctocyon13, Lophiodochcerus14, Pleura-spidotherium15, Pachynolophus maldaniie, Protodichobune owenii17. Thirdly, from Riitimeyer's ' Eociine Siiugethierwelt von Egerkingen' 18: Ailuravus19, Pelycodus helveticus20, Hyopsodus21, "Plesiadapis? "22, Acotherulum23, Cebochcerus2i, Lophiodon parisiense2*, Paloplotherium magnum 26; the last two only so far as their milk-teeth are concerned. I wish 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 Hydrochcerus, Phacochcerus, 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 Hystrix, for instance, seems rather more complex than the rooted molar of Erethizon, but on examining unworn grinding-teeth of Hystrix, 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 consequence 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. Contrary to Owen27, and all later palaeontologists, with the only 1 ' The Vertebrata of the Tertiary Formations of the West,' pi. xxiv. e. fig. 22. 2 L. c. pi. xxiv. g. fig. 6. 3 L. c. pi. xxv. e. fig. 12. 4 L. c. pi xxiii. d. figs. 14, 15, pi. xxiv. g. fig. 5. 5 L. c. pi. xxiii. g. fig. 12, pi. xxix. d. fig. 2-4. 6 L. c. pi. lvi. f. figs. 1 a, 2 a. 7 L. c. pi. 1. fig. 3. 8 L. c. lvii. b. fig. 1. 9 L. c. pi. xxv. e. fig. 13, pi. xxix. f. fig. 1 a, pi. lvii. f. fig. 8. 10 L. s. c. 11 L. c. pi. x. fig. 4. 12 L. c. pi. x. fig. 2. 13 L. c. pi. x. figs. 14,18,20, 22, &c. 14 L. c. pi. xi. fig. 129. 15 L. c. pi. xi. fig. 87. 16 L. c. pi. xi. figs. 117, 118. 17 L. c. pi. xi. fig. 132. 18 L. s. c. 19 L. c. pi. vii. figs. 18, 19. 20 L. c. pi. viii. fig. 1 (partim). 21 L. c. pi. viii. figs. 7, 8. 22 L. c. pi. viii. figs. 16, 17, 21. 23 L. c. pi. iv. figs. 22, 24. 24 L. c. pi. iv. fig. 30. 25 L. c. pi. i. fig. 8 (d3 sup.). 26 L. c. pi. i. fig. 1 (d sup.). 27 Rich. Owen, " Description of the Cavern of Bruniquel aud its Organic Contents. Part II. Equine remains " (Phil. Trans, vol. 159, London, 1870, p. 537). PROC. ZOOL. Soc-1893, No. XIV. 14 |
