296 PALAEONTOLOGY OF ILLINOIS. 



zontal shoulder, posterior face neai'ly plane or slightly beveled below, 

 laterally abruptly truncated and angular, interior surface broad and 

 flattened in nearly the same plane as the crown, both sides coarsely 

 roughened. Crown equaling the greater diameter of the base, strong, 

 linear, slightly constricted interiorly, extremities very gently curved 

 forward and abruptly truncated vertically, crest nearly central, sharp, 

 even, or in some examples produced into a slight submedian prominence, 

 outer and inner faces nearly equal in bight and gently arched vertically, 

 in the outer face bounded by delicate coronal plica? forming a belt 

 ascending obliquely from the basal border to the upper coronal angles, 

 constituting the only semblance of basal folds ; both faces are similarly 

 ornamented with numerous angular, slightly deflected or divergent ver- 

 tical ridges, irregularly bifurcated below, with short implanted ridges 

 extending downward from the crest, sometimes more or less interrupted 

 in their direct course, producing a delicate and singularly beautiful 

 sculpturing, and covered by a dense enamel-like layer. Length of 

 medium-sized specimen .19 inch, bight .OS, elevation of crown .03, 

 greatest autero-posterior diameter of crown . 04 inch. 



Of the present form we have examined only two examples, and the 

 identity of one of these (an imperfect tooth which exhibits certain pecu- 

 liarities in common with the type), is not well established. The form of 

 the individual teeth readily distinguishes them from other species of 

 Orodus ; but this very peculiarity, and the manner in which the speci- 

 men occurs, has led us to question its generic identity. The type con- 

 sists of two teeth, in every respect perfect individually, but which are 

 firmly united at their bases ; the inferior surface of this basal plate is 

 evidently no part of the ossified mandibular support, on the contrary, 

 it always constituted the inferior surface of the bases of the teeth, as 

 shown by the presence of a faint suture indicating the margins of inde- 

 pendent teeth. It is hardly probable that the two teeth in the example 

 described constituted the complete row, which was doubtless made up 

 of several additional individuals; yet there is not the slightest evidence 

 of other teeth having been as intimately connected with them as they 

 are with themselves — there being no fracture or other sign suggesting 

 such intimate association. Hence, it would appear that, under certain 

 conditions, the consolidation of two or more contiguous teeth by the 

 impingement of their bases, which are soldered into a common basal 

 support, may be effected, and the occurrence of specimens in this con- 

 dition, therefore, may not indicate a departure from the normal condi- 

 tion of more than abnormal importance. 



The peculiar evenness of the coronal crest, which, in the type, is des- 

 titute of median prominence, though such a character is more distinctly 

 exhibited in the doubtfully referred specimen previously mentioned 



