638 FOSSIL MAMMALIA IN" MODERN 



whales, have recently been found at Felixstow, in what is called " the 

 detrital bed," so rich in phosphate of lime used in agriculture. That 

 accumulation of drifted materials lies at the base of the Red Crag, and 

 it has been supposed that the imbedded mammalian fossils were derived 

 from the destruction of an older set of strata. But in regard to the 

 Mastodon above mentioned, Dr. Falconer, who has devoted fifteen years 

 to the study of the fossil and recent Proboscideans, assures me that the 

 fossil is a well-known Pliocene animal, first observed in Auvergne by 

 MM. Croizet and Jobert, and called by them Mastodon arvernensis. 

 Cuvier did not adopt this name, for he had seen but a few specimens 

 from Auvergne, and he confounded it with M. angustidens. The entire 

 skeleton of both these Mastodons having now been obtained, they are 

 found to be referable to two distinct sub-genera. The Crag fossil be- 

 longs to the Tetralophodon of Falconer, a sub-genus of which five spe- 

 cies are known, so called because there are four ridges in the penulti- 

 mate true molar as well as in the two teeth which are placed immedi- 

 ately before it in both jaws. The Mastodon angustidens, on the other 

 hand, belongs, with six other species, to the section called Trilophodon, 

 in which the corresponding teeth have each three ridges. This Masto- 

 don, according to MM. Lartet and Falconer, is characteristic of the 

 Faluns and of the Molasse at Sansan at the foot of the Pyrenees, and 

 of several other Miocene localities.* 



The Mastodon arvernensis is, according to Dr. Falconer, the only one 

 yet found in England. It abounds with the Hippopotamus major in 

 the Pliocene strata of the Yal d'Arno, as well as in strata of the same 

 age in Piedmont and at Montpellier. It may be considered, therefore, 

 as a characteristic Plioceue species ; and this view is in accordance with 

 the fact that its remains are best preserved in freshwater strata, asso- 

 ciated and coeval with the Norwich Crag. But we have no evidence of 

 its surviving in England till the still more modern epoch of those flu- 

 viatile deposits in the valley of the Thames in which the Hippopotamus 

 major and a species of monkey, Macacus pliocamus, have been detected. 

 These freshwater strata are alluded to in the text (p. 153), as occurring at 

 Grays in Essex, 21 miles below London, and at Ilford, Erith, and other 

 places bordering the Thames. They consist of sand, gravel, and loam, 

 from 60 to 100 feet thick, and often form a terrace on each side of the 

 valley, rising to a much higher level than a vast bed of more modern 

 gravel, to which allusion will presently be made. At Grays, the Cyrena 

 consobrina of the Nile already mentioned, a shell common to the Nor- 

 wich Crag, together with several other shells no longer inhabitants of 

 Great Britain, and some of them unknown as living in any part of the 

 globe, occur, mingled with a vast majority of English species of land 

 and freshwater mollusca. The Cyrena, which I supposed till lately to 



° Professor Owen has given (Quart. Geol. Jour., Feb. 1856, p. 223), as a 

 synonym of the Crag Mastodon, the name of M. longirostrix, Kaup, a fossil of 

 the Miocene sands of Eppelsheim, referred by Falconer to the sub-genus Tetralo- 

 phodon. 



