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the bones of quadrupeds, and which are themselves of very high 
antiquity ; such as the beds of gypsum, at Paris ; since these rest on 
the more common shelly limestone, beneath which is the chalk. 
The larger cavities of the bones are filled by the same hard grey 
limestone ; but the pores and smaller cells are filled by a semi-trans- 
parent spar, which has sometimes a yellowish tinge. In general a 
thin coat of pyrites is seen to line the cavity, and, of course, to im- 
mediately 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 succeeding teeth. In this specimen are also discoverable the 
sutures which divide each branch of the jaw into six bones. An out- 
line 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 connected 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 circumstance, the outer lines formed by the 
branches, separate gradually from the part where they are united ; 
whereas, in the Gavial, they separate by a sudden and very sensible 
flexion. 4. The notch which separates 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 does not appear, in 
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