PEOZEUGLODOlSr. 251 



behind and external to the sockets of i. 2 and i. 3 there are slight pits for the reception 

 of the tips of the lower incisors. The canine, represented by its alveolus only, was a 

 very large tooth, much larger than the incisors : this seems to be a primitive character 

 inherited from the Creodont ancestor. The first premolar is a single-rooted tooth, 

 separated from the canine by an interval of about I'S cm., in which, to the outer side, 

 is a pit for the lower tooth. In the skull described, pm. 1 is just being cut, its point 

 appearing in the middle of the alveolus of the deciduous tooth it is replacing ; this seems 

 to be the first instance in which any indication of a succession of teeth has been observed 

 in the Zeuglodonts. The second premolar is separated from the first by an interval of 

 1'5 cm., occupied by a deep pit ; it is a double-rooted tooth with a strongly compressed 

 high cutting-crown ; the anterior edge bears four or five small serrations, while on the 

 hinder edge are two larger accessory denticles and a third smaller one belonging to the 

 cingulum. Behind, and to the inner side of the posterior root of this tooth there is a 

 deep fossa for the lower tooth. The third premolar is also a large high cutting-tooth, 

 the crown of which is similar to that of ^m. 2, except that on its inner side a little 

 behind the middle point there is a prominent enamel-covered buttress, projecting 

 inwards and backwards and supported by a large distinct root ; the presence of a third 

 root in this and the following tooth distinguishes this genus from Zeuglodon. In one 

 specimen there is also a small accessory root on the outer side of the tooth between 

 the two main outer roots. The last premolar differs from pm. 3 in having a more 

 molariform crown, the posterior border sloping much less steeply away and the three 

 posterior denticles rising nearly to the same height; on the anterior border the two 

 accessory denticles are larger than on the anterior teeth. This tooth also has a large 

 inner buttress and root. The first molar is considerably smaller than pm. 4 ; there 

 seems to have been only one accessory denticle on its anterior border, while behind 

 the main cusp there are two rising to nearly the same height, so that the edge of the 

 posterior part of the crown is nearly horizontal. This tooth also hadapostero-internal 

 buttress, but it is relatively smaller than in the posterior premolars, and it is not clear 

 whether it had a distinct root or is borne on the inner part of the transversely 

 elongated posterior root, imperfectly divided by a vertical groove. 



If these teeth be compared with those of Protocefus, they are found to be widely 

 dissimilar. In that genus the dentition, so far as the premolars and molars are 

 concerned, is practically that of a Creodont, the serration of the cutting-edges of these 

 teeth, so characteristic of the later Zeuglodonts, not having been acquired in that early 

 type. At the same time the posterior cheek-teeth (pm. B-m. 3) possess an inner (third) 

 root and distinct indications of an inner tubercle, both completely wanting in Zeuglodon. 

 In Prozeuglodon the structure of the posterior premolars [pm. 3, pm. 4), and probably 

 also oim. 1, is exactly intermediate, the characteristic serration having been attained 

 while the inner (third) root is not yet lost. The posterior molars seem to be lost, or 

 at least to be undergoing reduction. The large size of the canine compared with the 



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