. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. "^^ f^ >? 7^Q^ ifi, nve Figure 11. — Superior and inferior molars of Mesoluppus Batrdiix \- a series of unworn crowns of the upper and lower jaws. Scott has already pointed out that the incisors in this genus are simple, there being no indication of the infolding of the enamel, such as is seen in Anchitherium aurelianense. In some of the John Day species oi Anchitheruim the enamel is not in- folded, as observed in the lower jaw of a specimen referred to J. equiceps, Cope. The upper molars of Mesohippus clearly
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. "^^ f^ >? 7^Q^ ifi, nve Figure 11. — Superior and inferior molars of Mesoluppus Batrdiix \- a series of unworn crowns of the upper and lower jaws. Scott has already pointed out that the incisors in this genus are simple, there being no indication of the infolding of the enamel, such as is seen in Anchitherium aurelianense. In some of the John Day species oi Anchitheruim the enamel is not in- folded, as observed in the lower jaw of a specimen referred to J. equiceps, Cope. The upper molars of Mesohippus clearly show the first step in the formation of the posterior pillar, pp, which is so conspicuous a feature in Anchitherium, in the posterior valley. This can also be observed in a still simpler stage in a specimen of Anc/iilophus from the French Phosphorites. Step by step with the development of this cusp appears the posterior pillar, p, in the lower molars, behind the entoconid ; til is accessory cusp can be traced back to the teeth of Epihippus. When it finally unites with the en- toconid, in Hipparion, it forms the posterior twin cusp (6, h, Riitimeyer), which is analogous to the anterior pair formed by the union of the metaconid and anterior pillar, a (a, a, Riitimeyer). Thus the tran-sition from the Mesohippus to the Anchitherium molars is very gradual, as shown in the accompanying figures. By tracing back the rise of. /ict. me Figure 12. — Superior mo- lar of Anchillii'viiim Inni/i- crifte X -}. Superior and external view. Cope col- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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