E. T. Newton — Pre- Glacial Mammalia. 257 



explain it in the present notes. It will be sufficient to sa}'^ that in 

 1869 M. G-ervais (Zool. et Paleont. General, p. 80), adopted M. 

 Pomel's name of Dinbrotlcus Schmerlingii for these large " Forest 

 Bed" Beavers, believing that their affinity with Fisher's Trogontherium 

 had not been established. Prof. Owen, however, in 1869 (Geol. 

 Mag. Vol. VI. p. 49), described other specimens of these Eodents, and 

 being still convinced that his previous determination was correct, 

 retained the name of Trogontherium Cuvieri. Since that time several 

 examples of upper- and lower-jaw teeth, with limb-bones, have been 

 obtained, and it is with no little satisfaction I am able to say, that 

 these confirm, in an unexpected manner, Prof. Owen's determination. 

 Fisher's type specimen was a skull without the lower jaw and 

 having the cheek teeth in an early stage of wear, so that each 

 exhibited four folds or islands of enamel ; the hindermost one having 

 two small additional folds. The first British specimens found were 

 lower jaws, so that it was extremely difficult to compare them, 

 especially as neither of them had the teeth in the same early con- 

 dition of wear as the type. The only upper jaw with teeth which 

 was known, until quite recently, was that figured by Prof. Owen in 

 1869 (loc. cit.), and in this the only two teeth which were perfect 

 had each only two folds, and consequently differed much from the 

 original siDecimen. On this account several writers were of opinion 

 that they could not be referred even to the same genus. An exami- 

 nation of the numerous teeth, both lower and upper, which are now 

 to be found in various collections, show in a most conclusive manner, 

 as it seems to me, that the folds of enamel, which in the early con- 

 dition are all connected with the exterior siarface of the crown, 

 rapidly lose their connexion and become isolated, as is the case with 

 most of the folds in Mr. Fisher's type. Gradually as the tooth 

 wears some of the islands of enamel become obliterated, and hence 

 in old examples some of the teeth may exhibit only two folds, as in 

 the upper jaw figured by Prof. Owen and mentioned above. One 

 series of upper teeth, in Mr. Savin's Collection, agrees as closely as 

 possible with Fisher's original specimen as figured by Rouillier. 



The great difference, which Prof. Owen maintained there existed, 

 between this large "Forest Bed" Beaver and the recent forms of 

 Castor, is likewise confirmed by recent acquisitions. Not only do 

 these differences extend to the forms and proportions of the grinding 

 teeth and incisors, both upper and lower, but also to the form of 

 the lower jaw itself and to the bones of the limbs. 



There is no evidence of a second species of Trogontherium from 

 the "Forest Bed," all the remains at present found being referable to 

 T. Cuvieri. These remains have been obtained at Cromer, Mundesley, 

 Bacton, West Kunton, and Kessingland, and Mr. R. Fitch has an 

 incisor from the Norwich Crag of Thorj)e. 



Castor. — The remains of Beavers were among the earliest Mam- 

 malian bones obtained from the " Forest Bed," and were mentioned 

 by S. Woodward in 1833 (Geol. Norfolk), and referred to Castor fiber. 

 I have been unable to trace any remains of the true Beaver among 

 the older specimens, except one tooth in the King Collection, and 



DECADE H. — VOL. VIII. — NO. VI. 17 



