OCT 1 1800 



THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. VI. 



No. VII.— JULY, 1899. 



I. — Note on the Molar of a Trilophodont Mastodon from the 

 Base of the Suffolk Crag. 



By E. Eay Lankestee, M.A., LL.D., F.R.S., 

 Director of tbe jNTatural History Departments of the British Museum. 



(PLATE XI.) 



THE tooth tigiired in the accompanj'ino; plate was originally 

 noticed b}^ me in this Magazine thirty years ago, and was 

 more fully described b)' me a year later in the Quarterly Journal 

 of the Geological Society, 1870. p. 507. 



At that time it was in the collection of Mr. Baker, of Woodbridge. 

 It has since passed into the collection of the York Museum. I am 

 greatly indebted to the authorities of that institution for lending it to 

 me again for furtlier stud}', and for allowing me to remove from the 

 valleys between the transverse ridges of the tooth the remarkable 

 matrix which formerly filled them up. (Compare the figure in the 

 Quart. Journ. Geoh Soc, 1870, with that now published.) 



The interest attaching to this tooth is twofold. In the first place 

 it v/HS determined by me to be the upper penultimate molar of 

 a Trilophodont Mastodon, being a perfect enamel crown from 

 which no portion had been detached. It thus differs from the 

 well-known Tetralophodont Mastodon of the East Anglian area 

 (M. Arvei-nensis). Tiie completeness of the tooth-crown was 

 recognized by all the palteontologists who saw the actual specimen, 

 including the late Mr. George Busk, F.R.S., whose testimony on the 

 subject 1 cited. 



The second point of interest about the tooth is that its valleys 

 were filled by a matrix which I was able to identify with the 

 sandstone nodules called • box-stones,' the true nature of which 

 I had recently determined by collecting from every available source 

 the shell-casts and other organic remains which they contain. It 

 was shown that the ' box-stones ' which occur abundantly at the 

 base of the Suffolk Crag (and not in the Norfolk area) are the rolled 

 fragments of a Diestien deposit, in all probability an extension 

 of the Black Crag of Antwerp. The Trilophodont Mastodon was 

 therefore necessarily a tenant of the land surface before the 

 deposition of this Upper Miocene 'Black Crag.' In this respect it 



DECADE IV. — VOL. YI. — ^0. VII. 19 



