277 



% 



drupeds, and which are themselves of very high antiquity; such as the beds 

 of gypsum, at Paris ; since these rest on the more common shelly lime- 

 stone, beneath which is the chalk. 



The larger cavities of the bones are filled by the same hard grey lime- 

 stone ; but the pores and smaller cells are filled by a semi-transparent 

 spar, which has sometimes a yellowish tinge. In general, a thin coat of 

 pyrites is seen to line the cavity, and, of course, to immediately include 

 the spar : and sometimes the whole of these minute cavities have been 

 filled with pyrites. 



The most important specimen in the National Museum is a lower jaw, 

 nearly complete. This jaw, indubitably of a crocodile, is beset with 

 conical striated teeth, with the two sharp edges, one on the fore and the 

 other on the back part, and having the cavities for the germs of the suc- 

 ceeding teeth. In this specimen are also discoverable the sutures which 

 divide each branch of the jaw into six bones. An outline sketch of this 

 jaw is given Plate XVIII. Fig. 7. 



That this jaw belonged to some animal of the genus Crocodile, there 

 can be no doubt ; and the following differences, noticed by M. Cuvier, 

 as undoubtedly show that this animal could not be of the Gavial species: 

 1. The branches are much longer, in proportion to the anterior con- 

 nected part, than in either of the Gavials. 2. The branches do not form 

 so open an angle as in the Gavial ; the angle in the Gavial being about 

 60, and in the fossil jaw but little more than 30. 3. From this cir- 

 cumstance, the outer lines formed by the branches, separate gradually 

 from the part where they are united ; whereas, in the Gavial, they sepa- 

 rate by a sudden and very sensible flexion. 4. The notch which sepa- 

 rates the branches penetrates forwarder Between the teeth than it does 

 in the Gavial : in the Gavial there are but two or three teeth, and in 

 the fossil jaw there are seven in each branch. 5. The whole number of 

 the teeth is, however, less : in the fossil jaw there are only twenty -two 

 on each side ; whilst, in the Gavial, there are twenty-five. 6. There 



