EOTHEEIUM iEGTPTIACUM. — EOSIEEN LIBYCA. 209 



"Width of skull-roof at lambdoidal ridge 6-8 app. 



„ skull at middle of temporal fossse 3"6 



„ skull between ends of supraorbital processes ... 15 app. 



„ snout in front of narial opening 6-2 



„ narial opening 4*8 



Length of dental series from canine to last molar .... 14*2 



The dimensions (in centimetres) of the molars are : — 



Length. Width. 



m. 1 1-6 1-7 



m.2 1-8 1-9 



m.3 1-9 1-8 



The chief differences between this skull and that of Eodren are : — (1) the occipital 

 surface is wider and the lambdoidal crest more strongly developed ; (2) the supra- 

 temporal ridges are less developed, so that the skull-roof is less clearly marked off from 

 the temporal fossse ; (3) the cranial region is somewhat rounded ; (4) the nasals are 

 large, and must have overhung the nasal opening to a considerable extent ; (5) the 

 anterior incisors are not very much enlarged and have rather complexly folded crowns ; 

 (6) the second and third incisors, though shifted back close to the premaxillary suture, 

 are large and not displaced outwards ; (7) the canine is a large tooth on the alveolar 

 border; (8) the palate is less narrowed between the anterior premolars. The arrange- 

 ment of the nasals and the condition of the incisors and canines are the chief 

 primitive characters noticeable. 



Mandible (PI. XX. figs. 2, 2 a). — In the mandible of Eosiren the downwardly turned 

 symphysial region is greatly thickened, the anterior end of each ramus swelling 

 out into a rounded bulbous mass, which, uniting with that of the opposite side, 

 forms the massive symphysis. The line of union is marked ventrally by a deep 

 groove [sym.). The large mental foramen {m.f.) opens on the outer side of the 

 symphysis, and is continued forwards by a deep groove to the extremity of the jaw. 

 The rami are comparatively narrow from above downwards ; their alveolar border 

 is convex and their ventral edge concave, forming a regular arch from the symphysis 

 to the lowest point of the enlarged and rounded angular region. The coronoid process 

 arises from the outside of the ramus opposite the last molar which is in position, but 

 in front of a posterior alveolus-like depression, which seems to point to the existence 

 of a posterior successional tooth (see below). The upper portion of the coronoid 

 process, the articulation, and the posterior portion of the angular region are broken, 

 so that it cannot be seen whether any of the peculiarities described by Zigno in 

 Halitherium [Prototherium) veronense existed in the present species. The large 

 posterior aperture of the dental canal is situated on the inner surface of the expanded 

 posterior region a little behind the posterior end of the molar series. Just within the 



2e 



