ZEU&LODON ISIS. 



241 



Zeuglodon isis, a name also employed in his report on the Fayum and adopted here. 

 The large vertebrae, in the absence of proof to the contrary, will be regarded as 

 belonging to this species. 



C. 10208. Right ramus of mandible, imperfect posteriorly ; the premolars and molars are present, 

 though somewhat broken. Type specimen (text-fig. 78). The total length preserved is 

 about 83 cm. Anteriorly it terminates in a rounded extremity bearing the alveolus of 

 the first incisor ; externally it is convex in front, becoming flatter posteriorly ; internally 

 there is a flat symphysial surface extending back to about the middle of pm. 2. 

 The ramus deepens gradually from before backwards ; opposite i. 2 it is about 6-4 cm. 

 deep, while beneath m. 3 the depth is about 22 cm. In the anterior 26 cm. there are 

 the alveoli for four single-rooted teeth : z. 1 is situated at the extreme end ; i. 2 is 



Text-fig. 78. 



Eight ramus of mandible and premolar toolb of Zeuglodon isis: 

 A, outer side of mandible, -^ nat. size ; B, inner side of the first premolar, ^ nat. size. 

 i. 1-3, alveoli of incisors ; c, alveolus of canine ; m. 1-3, molars ; pm. 1-4, premolars. 



situated about 2 to 3 centimetres behind it, and has an antero-posterior diameter of 

 about 4 cm. ; L 3 is about 5"5 cm. behind i. 2, and its antero-posterior diameter is about 

 5 cm. ; the canine is about 4'5 cm. behind the last, and its alveolus is about 5 cm. in 

 diameter. The edges of the alveoli of these anterior teeth are very prominent. The 

 first premolar (^m. 1, text-fig. 78, A) is in situ ; it is a single-rooted tooth with a high 

 compressed crown curving rather backwards ; both its sharp anterior and posterior edges 

 are serrated, the posterior serrations being the coarser (see text-fig. 78, B) . The surface 

 of the enamel, especially on the inner side of the crown, is sculptured by a series of fine 

 more or less vertical ridges, which anastomose at intervals and do not run on to the 

 serrations of the posterior border, the surface of which is quite smooth. The height of 

 this tooth is about 6'5 cm., its antero-posterior diameter about 5 cm. Fm. 2 is 

 separated from pm. 1 by a space of 5 cm. ; it is a large double-rooted tooth with 

 serrated anterior and posterior edges ; the number of the serrations cannot be made out ; 

 the enamel both on this and the succeeding teeth is sculptured like that of pm. 1. The 



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