384 FOSSIL FISH. 



the fish must have been covered some instants after their 

 death, by the deposition in which they are found. One of 

 those fossil fish, to be seen in the galleries of the Paris Museum, 

 and which is supposed to be a blochius, had not time before its 

 death to let go another fish, which it was in the act of swal- 

 lowing. 



In some climates, when a fish, and particularly one furnished 

 with an air-bladder, dies in summer, it remains at the bottom 

 of the water for three or four days ; then rises to the surface, 

 even before it begins to be offensive, and does not sink to rise 

 no more, but when the parts which constituted it are disunited 

 by putrefaction. Most assuredly if some days had passed 

 between the death of the blochius just mentioned, and its 

 involvement in the crystallization where it was found, it would 

 have mounted to the surface of the water, and would have 

 been separated from the fish which it swallowed, when it was 

 surprised by the catastrophe which destroyed it. 



If we had not this example evidently proving the rapidity of 

 this catastrophe, we might mention other fishes found in the 

 same place, in the bodies of which were seen the skeletons of 

 those which they had swallowed. This would prove that they 

 had died suddenly, after having satisfied their appetite. 



It is not, therefore, astonishing to find so few fossil fish in 

 the shelly strata which have been formed in the bottom of the 

 sea and without catastrophe ; and those which are found there 

 must have been covered, shortly after their death, by a stratum 

 of sand, which concealed them, and hindered them from rising 

 to the surface. 



The remains of fish differ in so remarkable a manner, ac- 

 cording to their localities, that a person well exercised in this 

 sort of investigation can determine, from the nature of the 

 trace, the place from which an ichthyolite has come. The 

 same observation nearly holds good respecting the substance 

 into which they may have been converted. Thus the bones of 

 fishes are calcareous, siliceous, or pyritous, invariably accord- 



