248 MR. E. T. NEWTON ON TROGONTHERIUM CUVIERI. [Apr. 21, 



cuvieri from the Forest-bed of East Runton, near Cromer, of which 

 the following is an abstract : — 



In the year 1846 Sir Richard Owen referred certain Beaver-like 

 jaws and teeth from the Cromer Forest-bed to the Trogontlierium 

 cuvieri of Fischer, and although some doubt was thrown upon this 

 reference he maintained the correctness of his determination in 

 1869, when describing some further remains of this rodent. The 

 type of Fischer's Trogontlierinm being a skull, it was very desirable 

 that a similar specimen should be found in the Forest-bed, which 

 could be compared with it ; but hitherto the only parts of skulls 

 which have come to hand have been mere fragments. Recently, 

 however, Mr. A. Savin, of Cromer, has obtained a nearly perfect 

 skull from East Runton, and it is this which is fully described in 

 the present communication. A comparison with the skull of a 

 Beaver (Castor) shows that although in a general way resembling 

 it, yet the differences are certainly of generic importance. One of 

 the chief points of difference is found in the structure of the cheek- 

 teeth ; for while in the Beaver the enamel-folds are open to the 

 exterior of the teeth down to their bases, in the Trogontlierium 

 they are open for only a short distance from the summit, and 

 consequently with wear they are soon separated from the exterior 

 and form islands of enamel, some of which may become obliterated 

 at a comparatively early stage. It follows from this that well-worn 

 teeth may have fewer enamel-folds than others in an earlier stage 

 of wearing, a fact which has led to errors in the determination of 

 the affinities of this fossil rodent. 



When compared with the type skull of Trogontlierium, this 

 Forest-bed specimen is found to agree so closely with it in form and 

 structure, as well as in the arrangement of the enamel-folds of the 

 teeth, as to leave little doubt as to their specific identity. And a 

 further comparison with the Conodontes boisvilleltii of Laugel, from 

 the Pliocene of Saint Prest, reveals no diflference of specific value. 

 The study of this new specimen from the Cromer Forest-bed thus 

 confirms Sir Richard Owen's reference of these English and French 

 rodents to the Trogontherium cuvieri of Fischer. 



This memoir will be published entire in the Society's 'Trans- 

 actions.' 



The following papers were read : — 



