44 Mr. A. S. Woodward on the 



most typical examples of the lower dentition of 31. striatus in 

 the straightiiess of the median plates — a character scarcely 

 sufficient to justify specific separation. It is quite possible, of 

 course, that it repi'esents a form in which the successive sta,s:es 

 of the dentition " run parallel," so to speak, with the earlier 

 stages of M. striatus^ and yet indicate an animal of much 

 smaller dimensions when adult. But if so, it requires more 

 than the present pal?eontological evidence to establish the 

 fact, and M. Edivardsii must therefore be provisionally 

 regarded as a synonym of the species under consideration. 



More uncertain are the relationships of the fossil described 

 by Agassiz as the type of M. goniopleurus *. This, there 

 can be no doubt, is a fragment of a lower jaw. It is a much- 

 rolled specimen from the London Clay of Sheppey, having 

 approximately the dimensions of no. VII. of the foregoing 

 list, but differing in the more raised contour of the crown ; 

 and it is noteworthy that the British Museum collection com- 

 prises no other corresponding fragment from the same forma- 

 tion and locality. 



Of the upper dentition of M. striatus no particulars have 

 hitherto been published, and, compared with the lower jaw, 

 it appears to be represented by but few specimens in the 

 National Collection. It is, however, impossible at present to 

 distinguish with certainty the earlier stages of these teeth 

 from the upper dentition of M. toliapicuSj and we cannot 

 venture to publish measurements of more than the following 

 five specimens. It is not improbable also that the small fossil 

 shown in PL I. fig. 10 may be placed in the same series ; 

 and, if this determination be correct, it is interesting as 

 revealing the characters of all the three rows of lateral teeth. 



Upper Dentition o/" Myliobatis striatus. 



Eatige 



Myliohatis toliapicus^ Agassiz. 



1833-43. Myliohatis toliapicus, Agassiz, Poiss. Foss. vol. iii. p. 321, 

 pi. xlvii. figs. 15-20. 



• L. Agassiz, torn. cit. p. 319, pi. xhii. %s. 9, 10. 



