BEDS OF THK I'ERMIAX EI'OC'II IN XOIITH AJIERICA. 291 



The muzzle is quite piomincnt, a cluiracter somewhat exaggerated in the speci- 

 men by pressure. The nostrils are large, lateral in dii'ection, and situated close to the 

 end of the muzzle. The orbits are subround, of medium size, and look mainly up- 

 wards in the present condition of the specimen. Oue of tlie most important peculiar- 

 ities of the species is the disproportionately large size of the first or anterior incisor or 

 l)rcmaxillary tooth. The crown is conical and nearly straight, with an acute apex 

 slightly posterior to the central point. Its section at the base is slightly angulate. 

 The two other prcmaxillaiy teeth arc much smaller, the third quite minute and with 

 a sharp apex. 



Thei'p are three maxillary teeth separated by rather wide interspaces anterior to 

 the large tooth which gives character to the genus. Tlie latter is abruptly large, but 

 not equal in dimensions to the large first incisor. Posterior to it the maxillary teeth 

 are closely placed, and with obtuse crowns. They commence very small, and increase 

 in size posteriorly. At a point where the palatine or ectopterygoid, as the fact may 

 be, joins the maxillary, the tooth-bearing surface is wide, and supports four rows of 

 small obtuse-crowned spaced teeth of equal size. This dental patch is triangular, with 

 its long angles extending anteriorly and posteriorly. The latter angle terminates a 

 little posterior to the middle of the orbit. The teeth have a small axial pulj) cavity, 

 and the dentine is perfectly simple. 



The head sculpture is well defined, and is reticulated in pattern. 



Measurements. M. 



Length from end of muzzle lo posterior border of orbit, .054 



Transverse diameter of orbit, .016 



" " inlerorbital space, .020 



Length from end of muzzle to orbit, .034 



Vertical diameter of nostril, .008 



Vertical depth of maxillary in front, .018 



Length of first premaxillary tooth, .006.5 



Transverse diameter of do., .0038 



Distance between first incisor and large maxillary teeth, .013 



Distance from large maxillary tooth to posterior angle dental p;itch, .024 



Width of dental patch, .010.5 



Elevation of a posterior tooth, .0015 



This species is intermediate in size between the E. ordmatiis, wliicii is small, and 

 the M Of/uti, which is large. In its disproportionate inecpiality in the size of its 

 teeth, it differs from the latter; while the former has larger orbits and a difierent sculp- 

 ture, besides having half the linear measurements. The sculpture of the JEl ordtnatiis 

 is in parallel ridges, enclosing minute deep punctiform pits between them. 



A. p. S. — VOL. XVI. 2k. 



