342 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



Professor Owen, in his ' British Fossil Mammalia/ gives a very 

 beautiful representation (p. 291, fig. 101) of a fragment of a tusk 

 discovered by Mr. Fitch in the Mammaliferous Crag-pits near Nor- 

 wich. He describes it as a portion of the lower tusk of the Masto- 

 don angustidens. The specimen is about 15 inches long, with a 

 greatest diameter of ^^ inches. It is of a straight, compressed, coni- 

 cal form. The fragment is crushed, and it is manifest that the outer 

 layers of the ivory are detached, and that the original tusk was of 

 a larger diameter than the specimen now exhibits. The marked 

 conical form and great size are irreconcileable with this fragment being 

 referable to an inferior incisor of the Simorre M. (Triloph.) angus- 

 tidens of Cuvier : and it would seem to me that it is equally irrecon- 

 cileable with being considered as a lower tusk of M. {Tetralo- 

 phodo7i) longirostris, for the symphysial beak required for the im- 

 plantation of a tusk of such magnitude would be enormous, and is 

 unknown among any of the species of Mastodon. Professor Owen 

 describes the specimen as being traversed from end to end by a sub- 

 central canal. The same character has been observed in the upper 

 tusks of other fossil Proboscidea, and is nowise characteristic of a 

 lower incisor. I consider that the specimen in question is not a 

 fragment of a lower, but of an upper tusk near the point ; and it 

 differs in no important respect from the undoubted upper tusks of 

 M. (Tetralophodon) Arvernensis seen in the Museums of Florence 

 and Turin, which are either slightly curved or twisted in a gentle 

 spiral direction, as represented in the figure given by Sismonda * 

 of the Dusino skeleton. 



In corroboration of this view, it may be stated, that the Indian 

 fossil species which we have named M. {Tetralophodon^ Sivalensis 

 is in some respects more nearly allied to the Crag species than the 

 latter is to either M. {Trilophodon) angustidens or M. (Tetralopho- 

 don) longirostris. It shows the same alternate character of the mam- 

 millse of the ridges of the " intermediate molars," and it appears 

 to have been equally destitute of inferior incisors. 1 have examined 

 a large number of lower jaws of this species, of all ages, from the 

 sucking calf up to the adult animal, specially with a view to the 

 detection of these teeth, and never observed the slightest indication 

 of their presence in any specimen, whether in the Indian fossil col- 

 lection of the British Museum, at the India House, or in the rich 

 series belonging to the Asiatic Society of Calcutta. 



This completes what I have to bring forward in the shape of de- 

 scriptive and comparative details, in order to indicate the most pro- 

 minent diagnostic characters derivable from the teeth and jaws of 

 the Crag Mastodon. I beheve that the differences of the three spe- 

 cies included by Cuvier under the name of Mastodon angustidens 

 will be found to be carried out through all the principal bones of the 

 skeleton. It would be wholly out of place to enter upon such os- 

 teographical particulars on the present occasion ; but a good idea of 



* Op. cit. tab. 1. figs. 4 & 5. 



