PALiEOMASTODON PAEVUS. 



163 



of a larger outer and a smaller inner tubercle ; there is a small intermediate tubercle 

 in the anterior valley, but otherwise accessory tubercles are wanting ; the enamel is 

 very smooth and the cingulum practically absent. M.2 is Irilophodont, but the last 

 ridge is much smaller than the others ; it consists of an outer larger and a smaller 

 inner cusp. So far as their molar pattern is concerned, both this species and P. headnelli 

 seem to be more primitive than P. wintoni ; but, on the other hand, P. headnelli by its 

 larger size, and both it and the present species in the elongation of the mandibular 

 rami, seem to be somewhat more specialized. This intermingling of primitive and 

 more specialized characters is to be expected in a group represented by several 



Eight ramus of maudibleof Falceomastodon ^parvus. Type specimen. About ^ nat. size. 



contemporary species and undergoing rapid change in a given direction, the final 

 product, in this instance Tetrahelodon or some closely similar form, being the resultant 

 of the various modifications, and in this case combining increased length of the 

 mandible with more complicated molar structure. 



Form. & Log. — Fluvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 



M. 8479 a. Right mandibular ramus, imperfect at both ends: pm.Z & 4 are greatly crushed and 

 m. 1-3 much -vvorn. Type specimen figured (text-figs. 50 C, 55) . The mental foramen is 

 beneath the anterior end of p7n. 3, and the posterior end of the symphysis is about 5"5 cm. 

 in front of that point. The dimensions of the teeth are given in the table on page 169. 

 The depth of the mandibular ramus beneath m. 2 is 7'2 cm., in front of /mi. 3 G"6 cm. 



Presented hy W. E. de Wwton, Esq., 1903. 



M. 8847. Almost unworn third lower molar. 



Presented hy the Egyptian Government, 1904. 



M. 8846. Eight upper molar (? second) almost certainly belonging to this species. 



Presented hy the Ecjyptian Government, 1904. 



Probably several of the smaller teeth and jaws in Cairo may belong to this species, but further 

 examination of the material there would be necessaiy to determine this. 



Y 2 



