DESCRIPTION OF PLATE IV. 



Mastodon (Tetralophodon) Arvernensis prom the Crag. 



The figures in this Plate have been copied from those by- 

 Mr. Eord in Plate XII., vol. xiii., of the Quart. Journ. Geol. 

 Soc, with which the memoir on Mastodon was originally 

 illustrated. They are rather less than one-fourth (two- 

 ninths) of the natural size. 



[The letters to the figures refer to the same parts as in fig. 1, PL III.] 

 Fig. 1. Mastodon {Tetralophodon) Arvernensis, from Ramsey, near 

 Harwich : plan-view of the germ of the penultimate true molar 

 from the right side of the upper jaw. (See page 33.) 



Fig. 2. The same tooth, seen in profile. A large Hanking mammilla is 

 seen to occupy the middle of each valley. This specimen is in 

 the collection of the Rev. J. R Marsden, Great Oakley, Essex. 



Fig. 3. Mastodon {Tetralophodon) Arvernensis, from Suffolk : plan- 

 view of the germ of the last true molar from the left side of the 

 lower jaw. (See page 31.) b, c, d, e, f, the five ridges 

 composing the crown, the mammillae of which are disposed 

 alternately. 



Fig. 4. The same tooth, seen in profile. 



[Figs. 3 and 4 are drawn from a cast in the Geological Society's 

 Museum ; the ' bourrelet ' being partly restored from a Crag 

 molar of similar age, also in the Society's collection.] 



