Dr. C. W. Amlrens — Extinct Egyptian Vertebrates. 405 



surface. The symphysial region is massive and spout-like. The 

 dental foramen is beneath pm. 3. The coronoid process arises 

 from the outer surface of the ramus beneath the anterior end of m. 3, 

 and has a thickened anterior border which often remains when the 

 rest is broken away (see Fig. 2o). The condyle is transversely 

 extended, and is convex in that direction as well as from before 

 backward. 



There are two pairs of lower incisors, the first being comparatively 

 small teeth crowded between the second pair, which are modified 

 to form lai'ge tusks and are triangular in section. The incisors are 

 procumbent. 



The first of the cheek-teeth (pm. 2) consists of a high, blunt 

 anterior cusp, and a low, broad shelf-like talon. The next (pm. 3) 

 has a high anterior crest which seems to be composed of at least two 

 united cusps, and in front of the ridge thus formed there is a small 

 antero-internal cusp. Behind there is a talon with a slight median 

 prominence. The next tooth (pm. 4) is similar, and is, therefore, 

 simpler than the succeeding first molar, which is bilophodont, each 

 ridge being evidently composed of two tubercles. On the outer 

 side there is a distinct cingulum, which on the hinder border of the 

 tooth broadens out into a narrow talon with a median tubercle 

 forming a small third lobe to the tooth. The next tooth (m. 2) 

 is similar, but the talon is larger. In the last molar the talon is 

 large and bears a transversely elongated cusp on its postero-internal 

 border. 



The molars show a strong tendency to assume a trilophodont form ; 

 in fact, the two last may almost be regarded as having already done 

 so. This circumstance, together with the fact that in both jaws the 

 second incisors are enormously enlarged, while at the same time there 

 is a tendency to suppress the others (the third lower having already 

 disappeared), incline me to believe that in this animal we have 

 a generalized forerunner of the Mastodon type of Proboscidean. 

 This conclusion is likewise supported by some points in the structure 

 of the skull and skeleton. As to the group of primitive mammals 

 to which McBritherhim is most nearly related, it is not possible 

 to arrive at any definite conclusion till all the available parts of the 

 skeleton have been examined, but perhaps it will be found to have 

 arisen from some, at present, unknown subdivision of the Amblypoda. 



Dimensions of Upper Dentition. (Figs. 2a and b.) 

 Approximate length of upper pm. and m. series ... 147 mm. 

 Approximate diameter of tusk ... ... ... 30 ,, 



Length of diastema ... ... ... ... ... 27 ,, 



Dimensions of Upper Cheek Teeth. 

 Length. Width. 



pm. 2 27 ram. ... 23 mm. (approx. 



pm. 3 



pm. 4 



m. 1 



m. 2 



m.3 



