172 ME. E. T. NEWTON ON A SKULL OE TEOGONTHEEIUM CUVIEEI 



tympanic bullae. The cast of the specimen has a deep hole in this region, which has 

 evidently been made by some instrument, and it seems very doubtful whether it 

 properly represents a natural fossa of the specimen. If there is a single fossa in the 

 basioccipital it will be an important difference between this skull and the English one ; 

 but the basal region is much hidden by the matrix, and it seems highly probable that 

 bone has been drilled away ; for it is very unlikely that two skulls agreeing so closely 

 in other particulars should differ so materially in this one point, and I am constrained 

 to regard this peculiarity as due to accident. It may be that a too great confidence in 

 the similarity between this skull and that of the Beaver led to an injudicious clearing 

 away of the matrix, which resulted in the removal of some of the bone at the same 

 time. The large fossa in the basioccipital of the Beaver is quite unlike that in the 

 cast, and the skull itself makes no nearer approach to Fischer's specimen than it does to 

 tliat from the Forest Bed. Paying due regard to all the circumstances, it seems to me 

 that, until this fossa in Fischer's type can be proved to be a natural one, Sir E,. Owen's 

 identification must be held to be correct, and these Forest Bed rodents regarded as 

 specifically identical with Trofjontherkim cuvieri. 



6. Comparison of the Forest Bed Skull with that of Conodontes boisvillettii. 



The type specimen of Conodontes hoisvillettii was found in the Pliocene deposit at 

 Saint-Prest, and is preserved in the Ecole des Mines, Paris. This skull has been 

 figured and described by Gervais ; it has the three true molars in place, but wants the 

 anterior cheek-tooth (pm. 4) as well as the premaxillary bones. Some carefully 

 prepared casts of the surfaces of the teeth (fig. 8), which were kindly sent to me by 

 Prof. Daubree some years since, serve well for comparison, and show the teeth to be 

 somewhat smaller than the figures of them given by Gervais ; it seems, therefore, 

 that the entire figures given by the last-named author represent the skull a little 

 larger than its natural size, which would thus appear to be as nearly as possible the 

 same as the Forest Bed specimen. 



The hindermost tooth of C. boisvillettii (m. 3, fig. 8) has four folds of enamel, all of 

 which are isolated from the exterior of the tooth, and differs from the corresponding 

 tooth of the Forest Bed skull (m. 3, fig. 5) only in the absence of the small anterior 

 outer fold, which has doubtless been lost by wear. The first and second molars have 

 only two folds each, thus differing from the Forest Bed specimen, in which these teeth 

 have three and four folds respectively ; this difference, however, is due to the teeth of 

 the latter being somewhat less worn, the Saint-Prest specimen having lost by wear 

 the anterior and posterior outer folds ; indeed the three teeth of this specimen agree 

 precisely with those in the maxilla already alluded to (fig. 6). 



The palate presents the closest resemblance to that of the Forest Bed skull ; there are 

 the same anterior grooves, just between the alveoli for the premolars, which run back- 

 wards about halfway along the palate ; each palatine bone has a similar pit, or foramen. 



