404 Dr. O. W. Andrews — Extinct Egy2:)tian Vertebrates. 



(Fig. 2b). Immediately behind the large incisor are two small teeth 

 (represented only by alveoli), the anterior one probably being the 

 third incisor, the posterior the canine ; behind this is a diastema of 

 some length (about 27 mm.). (Fig. 2a.) 



Fig. 2. — Dentition of Mceritherium, Lyonsi. One-fourth natural size. (A) Upper 

 teeth; (B) front of snout, showing the tusk-like second incisors; (C) left 

 ramus of mandible from outer side. 



The cheek-teeth are six in number. The anterior premolar (pm. 2) 

 consists of an outer wall composed of four blunt tubercles, of which 

 the middle two (protocone and tritocone of Scott's nomenclature) 

 are largest and subequal. The anterior (? parastyle) and posterior 

 (? metastyle) are smaller. The inner side of the tooth forms 

 a broad triangular shelf-like edge, worn into a concavity by the tooth 

 below. The next tooth (pm. 3) has two external tubercles (proto- 

 and tritocone) and a large inner tubercle (deuterocone). The 

 cingulum is well developed, and forms a shelf-like hollow on the 

 posterior border. The next tooth (pm. 4) is similar. The first 

 molar is bilophodont, but the crests, which are completely separated 

 by the transverse valley, are distinctly composed of two tubercles, 

 those forming the anterior one being the paracone and protocone, 

 those in the posterior the metacone and hypocone. The cingulum 

 is well developed on the inner and anterior border of the tooth, 

 less distinct on the posterior, and absent on the exterior border. 

 The next tooth (m. 2) is similar, the last is wanting in the specimen 

 described. 



The mandible is very solidly constructed, the rami being 

 thickened and very convex from above downward on the outer 



