VERTEBRATES. 313 



form of the individual teeth and their arrangement upon the jaws, we 

 observe unmistakable Hybodont affinities. 



The articular extremities of the jaw are not preserved, though frag- 

 ments of the substance of the cartilage are scattered through the rock- 

 mass upon which the teeth are imbedded. These cartilages were doubt- 

 less comparatively thin, the outer and inner folds giving away to the 

 pressure which flattened the rami, as shown in their present condition. 



The teeth are disposed in serial rows having a convoluted inrollment 

 from the inner to the outer border, and gradually increasing in size 

 from the posterior extremity to the row of large median teeth, anterior 

 to which the rows as regularly diminish in size towards the symphysis. 

 Posterior of the median row the ramus presents six to nine rows, the 

 extra three rows apparently not reaching the extreme outer borders, but 

 spreading over the inner portion of the jaw, the extreme posterior row 

 diminished to half the vertical extent of the fourth in the series, the 

 mature teeth of which present no perceptible difference, except in their 

 diminished size, to the teeth of the other rows. These teeth are remark- 

 ably uniform in their shape. They may be described as laterally elon- 

 gated, very slightly arched along the obtuse angle of the crest, and 

 slightly curved forward, the anterior end perceptibly slightly more 

 thickened than the opposite extremity, but without defined median 

 prominence. The crown, therefore, is very uniform in proportions, and 

 robust. The middle portion of the ramus is occupied by a row of pro- 

 portionately very large teeth, which differ from the posterior teeth in 

 having the outliue of the crest quite strongly arched vertically between 

 the extremities and produced into a strong, obtusely conical, eccentric 

 prominence which culminates at a point more or less posterior of the 

 middle of the tooth. It should be here stated that the teeth of the 

 posterior contiguous row also show faint indication near their posterior 

 extremities of an apical culmination, from which point the crown very 

 slightly tapers anteriorly. The teeth of the anterior portion of the 

 ramus are very similar to those situated posterior of the median row, 

 and of which there are eight, possibly nine rows, gradually diminishing 

 in size anteriorly, or in the reversed order to that mentioned above. 

 The teeth of the row immediately in advance of the median row are 

 distinguished from the teeth of the corresponding row next behind the 

 median teeth, by their slightiy greater length and more slender propor- 

 tions, very slight forward curvature, and the more marked definition of 

 the eccentric apical culmination, which is situated about a third, or less, 

 the distance from the posterior extremity. The teeth of the other rows 

 do not show the latter feature so distinctly, though it extends to the 

 third or fourth row, and in the latter there is a tendency to irregularity 

 in the more central position of the obscure apical point. The teeth of 



