. Bulletin of the British Museum (Natural History), Geology. 186 EAST AFRICAN CHALICOTHERES o^oO. Fig. 4. Right lower molars of Chalicotherium. a, C. pilgrimi, M[, BMNH. Mi2167. b, C. rusingense, Rusinga, F 3608. c, C. grande, Paris specimen from Sansan (left teeth reversed), d, C. grande, lingual view of M2, BMNH. M40821. e, C. styriacum, lingual view of M2, from cast, BMNH. M12112. All x J. Some of the isolated molars, and all the incomplete teeth, cannot be definitely sorted into second and third molars. Recourse was therefore made to probability paper, by which means and standard deviation
. Bulletin of the British Museum (Natural History), Geology. 186 EAST AFRICAN CHALICOTHERES o^oO. Fig. 4. Right lower molars of Chalicotherium. a, C. pilgrimi, M[, BMNH. Mi2167. b, C. rusingense, Rusinga, F 3608. c, C. grande, Paris specimen from Sansan (left teeth reversed), d, C. grande, lingual view of M2, BMNH. M40821. e, C. styriacum, lingual view of M2, from cast, BMNH. M12112. All x J. Some of the isolated molars, and all the incomplete teeth, cannot be definitely sorted into second and third molars. Recourse was therefore made to probability paper, by which means and standard deviations could be estimated, assuming equal numbers of M2 and M3 in the collection. Altogether, 5 independent specimens containing lower molars are referred to the large form, as against 22 referred to the typical form. The three molars are so much alike that a single description will suffice for all. There are two roots, flattened from front to back and inclined somewhat posteriorly. The posterior root is the stouter of the two, especially in M3, where its posterior surface is more rounded. The length of the roots on M2 and M3 is 20-24 mm- A low inter-radicular crest is present on the base of the tooth. Of the two V-shaped buccal cusps, the protoconid is a little lower than the hypo- conid and occupies a smaller area on the crown. The anterior crest of the protoconid falls rapidly as it passes in a curve along the anterior border of the crown, and at its lingual end it becomes a cingulum ledge anterior to the base of the metaconid. There is no paraconid, though a notch may be worn in the crest to give the appearance of that cusp. A narrow cingulum on the anterior edge of the crown does not extend to the buccal side of the protoconid. The posterior arm of the protoconid remains nearly horizontal, crossing the crown to join the metaconid. The latter cusp is higher than the protoconid ; its base extends forward so as partly to close the trigonid basin. Closely applied to the posterior s
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