ELASMQBRANCHII. 109 



Genus MYLIOBATIS, Cuvier. 



Dental plates belonging to this and allied genera are not 

 uncommon in the Nodule-bed of the Red Crag ; but as they are 

 mostly isolated and broken, it is not possible to say to which 

 genus they belong. Seeing, however, that undoubted examples 

 of Myliobatu and ^Etobatis occur in this deposit, it is better to 

 regard these fragments as parts of one or other of these forms. 

 It is highly probable that the specimens from the Coralline and 

 Red Crags referred to by Prof. Prestwich (Quart. Journ. Geol. 

 Soc., Vol. XXVII., p. 132, 1871) and Messrs. R. and A. Bell 

 (Proc. Geol. Assoc., Vol. II., p. 202, 208, 1872) as Zygobatis 

 Woodwardi are of this nature. I have been unable to find any 

 specimens from these deposits which could be certainly called 

 Zygobatis, and provisionally retain the name of Zygobatis 

 (Rhinoptera) Woodwardi only for the very doubtful specimens 

 recorded by Agassiz from the Norwich Crag. 



Many of the specimens are no doubt derived from the Eocene. 



MYLIOBATIS DIXONI, AGASSIZ. 



A portion of a palate in the Museum of Practical Geology 

 from the Red Crag Nodule-bed of Boy ton, including parts of four 

 dental elements, which are proportionately wide and convex, and 

 another specimen from the same horizon in the Ipswich Museum, 

 are believed to belong to Agassiz' (Poiss. Foss., Vol. III., p. 319), 

 Eocene species, M. Dixoni* and probably have been derived from 

 beds of that age. 



MYLIOBATIS TOLIAPICA, AGASSIZ. 



This species, which was established by Agassiz (Poiss. Foss. 

 Vol. III., p. 321) for a London Clay species, is represented in the 

 Nodule-bed of the Red Crag, by a specimen in the Museum of 

 Practical Geology, from near Woodbridge, which agrees with the 

 example figured by Dixon (Geol. Sussex, Plate x, Fig. 5), it has 

 six median plates and a double row of laterals on one side. This 

 specimen having been ground down some distance below the 

 natural surface, has the edges of the plates serrated, and thus 

 resembles the M. suturalis, Agassiz (Poiss. Foss., Vol. III., 

 Plate 46, Fig. 12) now included under the above species (Cut. 

 Foss. Fishes, B. M., p. 116). There is another specimen in the 

 same Museum from Waldring field, and a third in the Ipswich 

 Museum from the same horizon. All these specimens have 

 probably been derived from Eocene strata. 



