﻿48 



NORTH AMERICAN FAUNA. 



lower jaw, 12.7 mm. (0.50 in.); height at condyle, 3.3 mm. (0.13 in.); height at coro- 



noid process, 3.8 mm. (0.15 in,); length of uj^per tooth row, 6.86 mm. (0.27 in.); 



length of lower tooth row, 7.6 mm. (0.30 in.). 



" ^ , . , • • 2-2 . 1-1 1-1 3-3 14 



Dental formula : mcisors, ^ ■ canines, -^ -^ ; premolars, ; molars, = 32. 



The skull is thin and papery, heing evidently that of a young animal. The facial 

 portion is narrow and pointed; the brain, case is <|iiadrate, 11 attcncd above, but rises 

 al)ruptly at the frontal border, the forehead being suddenly depressed. 



The lower border of the zygomatic arch is curved upward; the upper border is 

 greatly expanded vertically, the upper border of the malar forming a high a:igular 

 process at the middle of arch; the zygomatic process of the 8(iuamosal is short, and, 

 with the malar, passes forward in a line nearly parallel with the axis of the skull, 

 with only a very slight outward curvature. The tympanic bulhe are enormously 

 expanded, having an antero-posterior length of 5.84 mm. (0,23 in.), and a transverse 

 breadth of 3.3 mm. (0.13 in.), their length fully equaling one-third of the length of 

 the skull. In other respects Ihe A entral aspect of the skull presents nothing peculiar. 

 The lower jaw is narrow, the coronoid process small, rising but little above the con- 

 dyle; the angle is well developed. 



The dentition is weak, the incisors and canines being very small, relatively to the 

 molar series. The outer upper incisor is about one-half the size of the inner; both 

 have a small outer cusxi at the base. The upper canine is about equal in size to the 

 anterior half of the upper ]n-emolar. The molars present nothing distinctive. The 

 lower incisors are slightly double-notched (trifid) ; the lower canines are very small ; 

 the tirst iiremolar is about half the size of the second. 



Ill liis original account of tlie genus Etideyma^ Dr. Harrison Allen 

 describes tlie skull and teeth as follows: 



SlciiU. — Brain-case low, quadrate, the height one-half the bimastoid diameter. 

 The metencephalon as long as mesencephalon and pro-encephalon. Sagittal crest 

 rudimentary, does not extend beyond a line answering to the ndddle of the zygoma — 

 the remaining portions of the posterior temporal crest widely separated — the ante- 

 rior not defined. Dorsum of face-vertex with a shallow concavity which is not 

 sharj)ly detiucd; orbit with inflated inner wall and rugose elevated upper border; 

 lachrymal tubercle marked. Infra-orbital canal short; the foramen on line with 

 interval between second premohir and lirst molar. Line of the upper margin of the 

 anterior nasal aperture if produced would intersect the second premolar; tymx)anic 

 bone apparently incomplete above. 



The paroccipital process bold, trenchant; sterno-niastoid impression dcepl}^ con- 

 cave; mastoid composed entirely of the squamosal element. Zygoma quite as in 

 Cori/norkinus — the squamosal part twice as wide as maxillary; spheno-i^alatine fora- 

 men present, of large size, Occii)ital crest trenchant. Tympanic bone greatly 

 inflated, equals one-third the length of the skull, not touching basi-occipital, or 

 basi-sphenoid ; excavate anteriorly. It extends to a line which answers to the 

 middle of the glenoid cavity. The mesopterygoid fossa as long as one-third the 

 distance from the posterior palatal border to the incisors. The sphenoidal foramen 

 is at the bottom of a deep recess. The coronoid process is round, small, raised 

 scarcely one-third the height of the ascending ramus; lower border of the horizontal 

 ramus near the angle slightly concave. The angle is raised from the plane on which 

 the mandible rests * * 



Upjjcr iecth. — Incisors contiguous, slightly inclined toward the median line, but 

 the lateral tooth separated from the canine by a moderate interval. Central incisor 

 cuspidate, with a small cuspule projected midway on the posterior surface ; a distinct 

 cuspnle also arises from the cingulum posteriorly. Lateral incisor one half the size 

 of the central, and cuspidate, with a small cuspule arising from the cingulum on 

 the anterior and a second on the posterior portion. Canine not larger than the 



