298 PALAEONTOLOGY OF ILLINOIS. 



■while fulfilling their functions during the life of their possessor, but 

 which becomes less and less noticable towards the inner or newer teeth 

 of the row, or those which have not been brought into position for use, 

 and the innermost one is nearly perfect. Wherever the crowns have 

 suffered abrasion, the surface presents a coarse punctate structure, 

 otherwise it appears to be enveloped in the usual polished enamel-like 

 layer. In outline as seen from above, the crown is moderately arched 

 backward, the lateral extremities more or less constricted at the base of 

 the great cone, thence very gradually diminishing towards the extremi- 

 ties where they are abruptly truncated ; viewed from the side, the gen- 

 eral outline is slightly arched, the median cone forming a conspicuous 

 conical, slightly eccentric prominence, with indications of irregularly 

 disposed subordinate tuberculations in the lateral wings, which appear 

 more strongly defined iu the larger inner teeth, apparently indicating 

 the gradual introduction of modifications in the coronal contour of teeth 

 found at different stages in the growth of the animal to which they 

 belonged ; the crown is sharply constricted along the basal line in both 

 faces, the smooth inbeveled portion bearing faint traces of a delicate 

 reticulated ornamentation, above which the coronal surfaces are occu- 

 pied by numerous rather strong more or less regular vertical folds, with 

 short plicae occupying the interspaces immediately beneath the crest, 

 and more slender ridges encircle the median cone, which latter is pro- 

 duced into a small callosity near the base in front at the point of 

 impingement with the preceding tooth; the crest forms an obtusely 

 angular or obscurely defined submedian line in the lateral wings, appa- 

 rently obsolete in the median cone, and in the majority of the teeth of 

 the series it is entirely obliterated by wear. Base equaling or slightly 

 exceeding in its greater diameter that of the crown, forming an oblique 

 plate which is flattened in the same plane as the crown below and 

 smooth ; produced along the inner margin and roughened by irregular 

 coarse vertical folds and pits, deeply channeled in front, with a narrow 

 shoulder extending just beneath the base of the crown. The following 

 measurements present the comparative dimensions of the second and 

 eighth tooth of the series : Greatest length .68 inch, and .25 inch, 

 breadth across median cone .15 inch, and .01 inch, Light at median cone 

 .13 inch, and .03 inch. 



The specimen herein described presents the anomalous feature of seve- 

 ral teeth of the same row so firmly united at their bases as to form a 

 contiuuous and solid basal plate, with, however, faint traces of sutures 

 indicating the individuality of the several component teeth, which, 

 taken separately, present no features by which they may be distin- 

 guished from typical forms of Orodus. Whether this condition is due 

 to chemical action subsequent to their deposition, and by means of 



