Dr. C. W. Andrews — New Egyptian Fossil Mammals. 563 



Length. Breadth. 



' m. 1 3-9 3 (app.) 



m. 2 ... 4-4 3-2 



m. 3 4-5 3-2 (app.) 



So far as its molar pattern is concerned, both, this species and 

 P. beadnelli seem to be more primitive than the other species 

 referred to below, but on the other hand P. beadnelli, by its larger 

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

 mandibular rami, appear to be more specialised. This intermingling 

 of primitive and specialised characters is to be expected in a group 

 represented by several contemporary species and undergoing rapid 

 change in a given direction, the final product, in this case Tetra- 

 helodon or some closely allied type, being the resultant of the 

 various modifications, and here combining the great elongation of 

 the mandible with increased complication of the teeth. 



The second group, in which the posterior border of the mandibular 

 symphysis is immediately in front of the anterior premolar and the 

 molars are complicated by the addition of accessory cusps, also 

 includes two species. Of these one, P. minor, has already been 

 described (Geol. Mag. [5], Vol. I, p. 115) ; the other is a much 

 larger form, and is important as being probably the commonest 

 of all the species ; for this the name P. wintoni is suggested, in 

 honour of Mr. W. E. de Winton, by whom the expenses of 

 my third collecting trip to the Fayiim were defrayed. It is 

 considerably larger than P. parvus and P. minor, but smaller than 

 P. beadnelli. From this last species it is also distinguished by 

 (1) the extension back of the symphysis so that its posterior end 

 is only just in front of the anterior premolar; (2) the position of 

 the mental foramen on the side of the symphysis instead of behind 

 it; (3) the greater complication of the molars and their greater 

 length in proportion to their width; the last lower molar consists 

 of three transverse crests and a distinct talon. The type-specimen 

 is a mandible with the incisors and posterior molars in situ. The 

 dimensions (in centimetres) of this specimen are : — 



Length from condyle to tip of symphysis 74 



Width of symphysis at narrowest 8 



Length of symphysis ... ... ... ... ... 21 



The dimensions of the teeth are : — 



Probably the greater number of the Palceomastodon rema,ins so far 

 collected belong to this species, but in the absence of associated 

 series of bones it is not possible to be sure of this, although it 

 appears that no mandibles of the type of P. beadnelli have been 

 obtained in the pits from which most of the specimens have been 

 collected. 



The above-named species will be described more fully and figured 

 in the forthcoming " Catalogue of the Tertiary Vertebrata of the 

 Faytm." 



