THE 



GEOLOGICAL MAGAZINE, 



No. LVL— FEBRUARY, 1869. 



OI^IC3-I3^J^Xj -A^iaTIOLIES^ 



I. — On the Distinction between Castor and Trogontberium. 

 By Professor Owen, F.E.S., etc. 



(With, a Double Plate, III.) 



ACOMPAEISON, with corresponding parts of existing species of 

 Castor, of specimens of mandible and mandibular teeth of a 

 large beaver-like quadruped, obtained from the fresh-water deposits 

 called the ' Forest-bed ' on the Norfolk coast, led me, in 1845, to the 

 conclusion signified by the adoption of Fischer's generic appellation, 

 Trogontherium, for the rodent, which seemed to exemplify " an ex- 

 tinct sub-generic type " of Castoridce.^ 



Subsequent acquisitions of a femur from the Forest-bed at Mun- 

 desley, by the Eev. John Gunn, M.A., F.G.S., and of a tibia from 

 the same formation and locality, by the late Eev. S. W. King, M.A., 

 F.G.S., together with portions of upper jaw with teeth, have yielded 

 confirmation of the above conclusion. 



The teeth in the portion of upper jaw in Mr. King's collection 

 (Fig. 1), answer to the second (m 1) and third (m 2) right side of the 

 beaver : part of the alveolus, and the root of the first grinder (j> 4), 



Fig. 1. 



Xm-U 



Portion of Right Upper Jaw and Molar Series, 

 Trogontherium Cuvieri, nat. size. (Rev. S. W. 

 King's Collection.) 



Copied from Cast of Molar Series of 

 Trogontheriutn Cuvieri, from the 

 Department de 1' Eure et Loire. 



1 " Britisli Fossil Mammals," 8vo. p. 18i. 



VOL. VI. — NO. LVI. 4 



