3,32 PALJE ONTOLOGY OF ILLINOIS. 



welded. The relative position of these accessory teeth is shown in the 

 figures. Io shape they are not unlike worn examples of the large tooth 

 to which they are attached, and though firmly cemented where they 

 impinge upon the central tooth, their basal outline is perfectly pre- 

 served by the presence of the deep groove shown in the side view of the 

 specimen ; they are much worn, and the character of the coronal region 

 is consequently indistinctly shown ; there would appear to be but a 

 single row of cusps, such as obtains in the variety illustrated in fig. 37, 

 PI. 8, an extremely abraded individual of which these accessory teeth 

 strongly resemble. At all events, we evidently here possess an inti- 

 mation of the relative position of three individual dental plates, since 

 it is difficult to conceive accident could have any share in their so sym- 

 metrical disposition ; and, further, it seems very probable that the inti- . 

 mate relation of two quite distinct varieties is hinted at at least. 



One of the most common varieties contained in the collections is that 

 represented in fig. 35, PI. S, a form which.it is not always easy to dis- 

 tinguish from the middle tooth of fig. 33. These teeth, however, 

 . always appear to be rights and lefts, as shown by the curvature in their 

 outline viewed from above. The basal region does not differ from that 

 of the tooth alluded to, but the crown presents a double row of alterna- 

 ting cusps, buc which are so intimately associated as scarcely to indicate 

 their real character, and which in the anterior portion of the crown 

 become still less distinct and finally merge into a single row towards 

 the extreme front. The unsymmetrical form of these teeth readily sug- 

 gests their identity with the accessory teeth in the specimen above 

 referred to. The latter form is quite variable in the minor details of 

 size and the number of cusps along the crown, but not to the same 

 extent as occurs in the form representing the median tooth, fig. 33, 



isolated examples of which, or those in which the accessory teeth have 

 become detached, show the cusps originating anteriorly in a single row, 

 diverging into two rows in the middle, and towards the posterior extrem- 

 ity presenting three such rows of cusps 



STE3DIATODUS SIMPLES. 

 PI. 8, Kg. 30,37. 



Teeth represented by four examples, showing similar outline to the 

 varieties last noticed above, apparently symmetrical, and in which the 

 cusps are arranged quite regularly in a single row. The tooth fig. 3G, 

 which preserves the enamel, shows no trace of striae, from which it is 

 inferred the cusps were smooth. The specimen just referred to'exhibits 

 the anomalous feature of the budding of an accessory arm bearing three 

 cusps, from one of the lateral surfaces about midway between the 



