NO. 1666. 



OSTEOLOGY OF CAMPT08AURUS—0ILM0RE. 



223 



crown and root to the upper border of the former. Every tooth 

 shows one pronounced longitudinal ridge, which is always, whether 

 it be upper or low^er, posterior to the median line, having on each 

 side a varying number of secondary ridges (fig. 9). There are more 

 of the secondary anterior to the main ridge than there are posterior. 

 The secondary ridges are also more numerous and stronger in teeth 

 of the upper than in those of the lower jaw, a character which serves 

 to distinguish detached teeth. Man}^ of these ridges subside before 

 reaching the base of the crown ; none are serrated as is the case in 

 the teeth of Igvanodon. The teeth at either end of the dental series, 

 whether it be upper or lower, are slightly smaller than those inter- 

 mediate. The contour of the larger teeth appears to be less angular 

 than the smaller. Both upper and lower teeth are curved longi- 

 tudinally, this curvature inclining the crowns of the upper teeth 

 inward to meet those of the lower jaw% Avhich are similarly inclined 

 outward. Nearly all crowns which project fully above the level 

 of the outer bor- 

 der of the alveolar 

 process show^narks 

 of wear, being ob- 

 liquely g r o u n d . 

 The ridged surface, 

 liaving thick en- 

 amel, stands longer 

 and forms a cut- 

 ling edge, which at 

 first is serrated, but 

 later becomes sin- 

 uous as the loniri- 



FiG. 10. — Internal view of right dextary, Camptosaukus 

 DiSPAR? MAR.sn. Cat. No. 5S10, U.S.N.M. I nat. .size. 

 a, anterior end ; h, dextary ; i), posterior end. 



tudinal ridges become cross sectioned. The inner surfaces of the 

 crowns are smooth, gently convex antero-posteriorly, and unsculp- 

 tured, the terminal marginal serration showang slightly upon it. 

 When much worn these spatulate teeth are reduced to flattened stumps, 

 as shown in the figures. Hulke" says of the teeth of Ilyfsilopliodon: 

 " By the time the crown is worn to the level of the aveolar border of 

 the jaw, the tapering cylindroid root has been absorbed, so that a very 

 slight force w^ould suffice to detach the remnant in this condition." 

 In Camytomurus^ however, they appear to be forced out before the 

 absorption of the root, as will be seen by an examination of figs. 8 

 and 10. 



The arrangement of the teeth in a longitudinal and vertical series 

 is well shown in figs. 8 and 10. Successional teeth in the dentary are 

 seen below and betw^een those of the functional row. In the maxilla3 

 these teeth descend as usual on the inner side of those in use. Thus, 

 in the upper jaw they replace on the unsculptured and in the lower 



"Phil. Trans. Roy, Soc. London, CLXXIII, 1882, p. 1042. 



