. Bulletin of the British Museum (Natural History), Geology. HE LIBYAN MIOCENE 497 There are few accounts of creodont brains for comparison; the brain of Megisto- therium retains a number of primitive characters, but displays in the cerebrum and cerebellum more complexity than is usual in creodonts. Dentition. The dental formula for the upper dentition is i i 4 3. This differs from normal hyaenodonts onl}^ in the great reduction of the incisors to one. The teeth are poorly preserved but sufficient survives to establish most of the salient features. The single incisor is very large and probably
. Bulletin of the British Museum (Natural History), Geology. HE LIBYAN MIOCENE 497 There are few accounts of creodont brains for comparison; the brain of Megisto- therium retains a number of primitive characters, but displays in the cerebrum and cerebellum more complexity than is usual in creodonts. Dentition. The dental formula for the upper dentition is i i 4 3. This differs from normal hyaenodonts onl}^ in the great reduction of the incisors to one. The teeth are poorly preserved but sufficient survives to establish most of the salient features. The single incisor is very large and probably the third; it is absent on the right and only the root remains on the left side. The transverse section of the tooth just below the base of the crown is egg-shaped, the point directed anteriorly. The incisors are closely juxtaposed and stand proud, anterior to the canines. The canine is missing on both right and left sides, but the alveolus betokens its enormous size, massive root and near circular transverse section. The first premolar is missing on both sides; it was a small single rooted tooth placed behind and slightly medial to the canine. The rest of the cheek dentition, P2 to M^, lies on a straight line; this line if continued anteriorly would pass through the incisor tooth on the opposite side. The angle between the line of the right and left cheek dentition is 50°. Almost the whole of the second premolar is preserved on the left side; the root is doubled and the crown single cusped. The crown of P^ is longer than broad, has a posterior keel, thick enamel, and the tip of the cusp is worn flat so that overall the tooth resembles P^ or P^ of Crocuta. Small diastemae separate P^ anteriorly and posteriorly from Pi and P^. P^-M^ form a tight series without any gaps between the teeth. Of P^ only the roots survive and the tooth is notable in possessing three roots, each of equal size; the internal root is opposite. c m, Fig. 10. Megistotherimn osteothlastes gen. et sp. nov.
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