TERTIARY VERTEBRATA OF THE FAYCM. 
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Ujt])er Dentition . — 'riierc are tliree pairs of incisors. The first, pair (PI, X. fig. 3, i. 1) 
are in close contiict in the middle line ; they are comparatively small, downwardly 
directed, ))rismatic teeth, each implanted in the premaxilla by a long backwardly 
curved root. Their transverse diameter is ronghly -8 cm. The second incisors (?. 2) 
form great downwardly directed tusks. Their anterior face is strongly convex, the 
posterior slightly flattened ; the tooth as a whole is strongly curved and tapers 
somewhat towards the root, which, in the adult at least, is closed. There is an oblique 
B. 
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X 5. 
Cast of the cranial cavity of Mceritherium hjonsi: A, from above ; B, from right side. 
c?;., cerebellum ; frontal lobe ; mf., pituitary body ; y)., pseiidosylvian depression ; o.Z., olfactory lobe; 
t.l., temporal lobe ; V., base of fifth nerve. | nat. size. 
wear-surface on the posterior side of the crown. No sufficiently well-preserved 
specimen has been found to show whether the enamel-covering was complete or not. 
In one skull these tusks project some 4’8 cm. from the jaw, but as their ends are 
broken off above the commencement of the wear-surface, it is probable that when 
complete they protruded at least half as far again ; in this specimen the antero- 
