292 PALEONTOLOGY OF ILLINOIS. 



beneath the crest in either face, the posterior slightly exceeding tbe 

 anterior face in elevation, gently constricted inferiorly, extremities 

 slightly produced laterally, crest acute, minutely denticulated, and 

 gradually ascending to the more or less eccentric median prominence, 

 which forms the apex of an obtuse angle, slightly deflected laterally 

 toward the shorter extremity, gently convex or distended in the middle 

 before and behind, supported in front by the moderately prominent 

 basal protuberance; the coronal faces are uniformly sculptured in 

 strong, sharp, closely arranged, sometimes bifurcated vertical ridges, 

 one, two or more of which culminate in the minute denticulations along 

 the crest, which latter are more or less irregularly developed, or varia- 

 ble in prominence, the extreme lateral ones sometimes quite prominent, 

 the interspaces are occupied by short thread-like lines descending from 

 exceedingly delicate denticulations iu the crest and rising from the base, 

 producing in the highly polished enameled surfaces the most exquisite 

 coronal ornamentation. 



The anterior teeth are smaller, typical examples averaging .4 inch in 

 leugth. The base is relatively more massive, less beveled or slightly 

 produced in front, inferior surface very gently arched upward, some- 

 times straight, plane, converging to the posterior margin, forming one 

 side of an equilateral triangle, of which the other two sides constitute 

 respectively the posterior and anterior corono-basal faces in the lateral 

 wiugs of the tooth. The average hight of the crown about equals the 

 depth of the base, it is slightly constricted inferiorly, rapidly converg- 

 ing to the crest, which is flanked laterally by somewhat stout, laterally 

 deflected, recurved denticulations, and thence, with intermediate lesser 

 and variable denticulations, approaches the abruptly produced, eccen- 

 tric median prominence, which is situated about one-third the distance 

 from one or other extremity, the sharp, rounded apex directed towards 

 the short extremity and recurved, in elevation as great again as the 

 lateral wings, lenticular in transverse section with sharp cutting edges, 

 the base in front somewhat in ore prolonged into the basal protuberance 

 and posteriorly notched than occurs in the median teeth; the coronal 

 sculpturing is the same as described iu the former variety, the chief 

 differences distinguishing the present one consisting in the relatively 

 more massive, inferiorly expanded base, the stouter denticles at the 

 lateral extremities, and more prominent, compressed median cone. 



Associated with the above varieties, a third occurs, which, more inti- 

 mately like the median teeth in form and general proportions, is distin- 

 guishable by its linear outline, the median prominence being scarcely 

 distinguishable, the body of the teeth being quite regularly and very 

 gradually attenuated from the short to the long extremity, the crest 

 interrupted by more or less widely spaced denticulations, the intervals 



