YEETEBEATES. 329 



from which the crown is defined by the more or less distinct termina- 

 tion of the enamel layer. See PI. 8, fig. 30. 



The second subgroup alluded to above, is represented by compara- 

 tively simple teeth, in which the basal region is much narrower, though 

 probably presenting much the same contour as in the precediug teeth, 

 but generally being worn to a rounded ridge below, gently arched 

 between the extremities, and" surmounted by a single row of coronal 

 cusps, which in shape and succession are much like one of the siugle 

 rows in the teeth above noticed. See PI. S, fig. 37. 



The intermediate forms', or those connecting the extremes above 

 described, are represented by (1) teeth possessing basal features gene- 

 rally preserved in the couditiou last noticed above, but which when per- 

 fect show a more or less deeply excavated inferior surface, bounded by 

 the walls of the lateral margin, and terminated anteriorly iu a down- 

 ward produced process, the crown occupied by two rows of teeth, the 

 cusps depressed and irregularly alternating. See PI. 8, fig. 32. (2.) 

 Teeth, represented iu fig. 33, PI. 8, in which the two rows of cusps are 

 less individualized, seeming to originate in a single row towards the 

 extreme front, though probably the two rows becoming merged in widely 

 spaced irregular alternating order, such as is maintained throughout 

 the crown in (3) the variety represented in fig. 35, PI. 8. The latter 

 teeth are also apparently in pairs, but those represented in figs. 32, 33, 

 appear to be symmetrical and therefore may have occupied a median 

 position. 



As to the nature of these little dental bodies, whether they pertained 

 to the jaws or other part of the mouth, it may not be possible conclu- 

 sively to decide. They may have occupied the tongue or back part of 

 the roof of the mouth, a supposition suggested at least by their resem- 

 blance to the dental plates of some of the Devonian ganoids, e. g., 

 Diptents ; while, on the other hand, they are not so strikingly unlike 

 the dental armature occurring on the jaws of Oeratodus. But the latter 

 suppositions, again, seem less probable on account of the occurrence 

 amongst these remains of apparently symmetrical teeth, so that, were 

 they referable to the maxillary elements, they must have occupied 

 the extreme anterior portion of the jaws, and hence indicating a fish 

 whose jaw extremities were not edeutalous. In the former position, 

 they may have occurred in pairs or threes, as also in case they belonged 

 to the anterior or symphysial region of the jaws. 



The several more or less distinct forms thus far observed are further 

 noticed below, where the several varieties are designated by a provi- 

 sional term, in the absence of data showing their true character and 

 relationship. 



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