FISHES OF MONTE BOLEA AND NAPLES. 101 



fresh-water from a bursting lake, or unusual land flood, is 

 often fatal to large numbers of the inhabitants of the waters 

 thus respectively interchanged.* 



The greater number of fossil fishes present no appearance 

 of having perished by mechanical violence ; they seem 

 rather to have been destroyed by some noxious qualities 

 imparted to the waters in which they moved; either by 

 sudden change of temperature,! or an admixture of carbonic 

 acid, or sulphuretted hydrogen gas, or of bituminous or 

 earthy matter in the form of mud. 



The circumstances under which the fossil fishes are found 

 at Monte Bolca seem to indicate that they perished suddenly 

 on arriving at a part of the then existing seas, which was 

 rendered noxious by the volcanic agency, of which the ad- 

 jacent basaltic rocks afford abundant evidence. The skele- 

 tons of these fish He parallel to the lamina? of the strata of 

 the calcareous slate; they are always entire, and so closely 

 packed on one another, that many individuals are often 

 contained in a single block. The thousands of specimens 

 which are dispersed over the cabinets of Europe, have 

 nearly all been taken from one quarry. All these fishes 

 must have died suddenly on this fatal spot, and have been 

 speedily buried in the calcareous sediment then in the course 

 of deposition. From the fact that certain individuals have 

 even preserved traces of colour upon their skin, we are cer- 

 tain that they were entombed before decomposition of their 

 soft parts had taken place.J 



* See account of the effects of an irruption of the sea intol'oe fresh-water 

 of the lake of Lovvestoffo, on the coast of Suffolk. Ediiiburg Philosophical 

 Journal, No. 25, p. 37:2. 



t M. Agassiz has observed that a sudden depression to the amount of 15° 

 of the temperature of liie water in the river Glat, wliich falls into the lake 

 of Zurich, caused the immediate death of thousands of Barbel. 



t The celebrated fish (Biochius longirostris) from this quarry, described 

 as petrified in the act of swallowing another fish (Ilhiolitologia Veronese, 

 Tab. XII.) has been ascertained by M. Agassiz to be a deception, arising 

 •from the accidental juxta-position of two fithes. The size of the head oftb« 



9* 



