[ 165 ] 



VI. On a Skull 0/ Trogontherium cuvieri _/rom the Forest Bed of East Banton, 

 near Cromer. Bij E. T. Newtox, F.G.S., F.Z.S., Geological Survey. 



Received March 17th, 1S91, read April 21st, 1891. 



[Plate XIX.] 



Contents. Page 



1. Introductory 165 



2. Description of the Skull of Tror/ontherium from East Euaton 106 



3. Dental Characters of the Tror/ontherium of the Forest Bed 170 



4. Comparison of thePorest Bed Skull with Fischer's Tror/onthenum euvieri 171 



5. Comparison of the Forest Bed Skull with that of Conodonles hoisnlhtlii . . 172 



6. Measurements 173 



7. Conclusions 17-4 



8. Bibliography 174 



9. Explanation of the Plate 175 



1. Introductory. 

 At the time when the Geological Survey Memoir on the Vertebrata of the Forest Bed 

 was published (1882), the parts of the skull of Trogontherium, which were known in 

 this country, were the maxillae and premaxillse, with incisors and cheek-teeth ; the only 

 example, however, of a last upper molar was the half tooth preserved, with the first 

 and second molars, in the maxilla described by Sir R. Owen \ which is preserved in the 

 King Collection in the Museum of Practical Geology. The imperfect condition of this 

 last upper tooth deprived us of one of the chief characters by which Trogontherium is 

 distinguished from Castor, and rendered the determination of the British specimens less 

 certain than it would otherwise have been; the available materials, however, were 

 sufficient to justify Sir R. Owen's reference of them to Trogontherium euvieri, a form 

 described by Fischer ^ from near the Sea of Azof. 



A skull of this rodent, from British deposits, has long been a desideratum, in order 

 that a close comparison might be made with the nearly perfect type skull ; and such a 

 specimen has now been secured from the Forest Bed of East Runton by Mr. A. Savin, of 

 Cromer, who has been kind enorigh to send it to me for identification and description. 

 In many particulars this specimen (Plate XIX.) is in a more satisfactory condition for 

 examination than Fischer's type, which is so much obscured by hard sandy matrix that 

 the relations of the bones cannot be clearly seen, while Mr. Savin's specimen is almost 

 free from matrix, and the surfaces of the bones, as well as the sutures, are well 

 displayed. 



' Geol. Mag. vol. vi. p. 49 (1869). = Moscow Soc. Nat., Mem. vol. ii. p. 250 (1809). 



VOL. XIII.— PART IT. No. 1. — April, 1892._ 2 b 



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