PLATE 49. 



MYLIOBATIDAE. 



Fig. 1-3. Aetob.^tus N.\RiNARi (Page 441). Fig. 4-6. Myliob.^tis c.\lifornicus (Page 429). 



1. Dentition of a very young .specimen. M. C. Z. 1079. 



2. Dentition of a young specimen, larger than that shown in fig. 1. M. C. Z. 107(1. 



3. Teeth of a large specimen. M. C. Z. 865. 



4. Dentition of a very young specimen. M. C. Z. 348. 



5. Dentition of a larger specimen. M. C. Z. 395. 



6. Dentition of a specimen beyond the age of rapid growth. M. C. Z. 424. 



In the youngest specimens of .\etobatus examined there are two rows of upjier and two rows of lower 

 teeth, fig. 1 and 2, each two quickly broadening and being succeeded by the broad teeth of the single 

 row retained through life. Possibly a still earlier stage may show a dentition more like that of Rhinop- 

 tera in its primary features. The earhest stage of Myliobatis figured has six rounded teeth in front of 

 the pavemeot, another has seven, thus accounting for all the rows of later stages, the median one only 

 becoming broad. It is to be expected that younger specimens wW show dentitions more in accord with 

 that of fig. 1, Plate 48, in Rhinoptera. 



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