THE TEETH OF REPTILES. 259 



tained. Moreover the maintenance of a sharp edge is further 

 secured by the dentine on the enamelled side of the crown 

 being of the hard unvascular variety, that on the inner being 

 vaso-dentine and therefore softer. The remnant of the pulp 

 ossifies, and comes into use, as these teeth remained at work 

 until worn quite to a flat surface. The root portion was 

 smooth, round, and curved. 



Professor Marsh (American Journal of Science, March, 

 1880) has described and figured a peculiar Dinosaurian den- 

 tition, in a reptile to which he gives the name of Stegosaurus ; 

 the teeth are slightly compressed transversely, and are 

 covered with a thin enamel ; the roots are long and slender, 

 implanted w^eakly in separate sockets. But at the inner side 

 of the roots of the teeth in use were no less than five suc- 

 cessional teeth, in graduated stages of development, ready 

 to ultimately take its place ; so large a number of successional 

 teeth has not hitherto been met with in a Dinosaur. 



A very remarkable carnivorous reptile as large as a lion 

 has been described by Professor Owen (Quart. Journal 

 Geolog. Society, 1876,) under the name of Cynodraco major 

 for the reception of which he proposes a new reptilian order, 

 that of Theriodontia. Its dentition is not completely known, 

 but it possessed in the lower jaw eight incisors, of which the 

 first is the smallest, and a canine of moderate size. The 

 upper incisors are not known, but there were a pair of upper 

 canines of such size that they extended down along the 

 outside of flattened portion of the lower jaw, like the 

 canine teeth of Machairodus. The hinder margins of these 

 canines were trenchant, and finely serrated. 



The Fterosauria, or flying reptiles, have, since the 

 discovery of toothed birds, become of special interest to 

 the odoiitologist. The wings were stretched membranes, 

 like those of a bat, and the measurement across their tips 

 in some of the largest must have been twenty-five 

 feet ; but most of those known were much smaller, from 



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