224 UPPER, OR FLINTY CHALK. 



Locality. Upper chalk, near Lewes. 



98. Leg of an unknown crustaceous animal. Tab. xxxiv. fig. 4. 



This fossil is part of the leg of some crustaceous animal, but whether 

 belonging to either of the genera above-mentioned cannot be ascertained ; 

 it is nearly black, and its surface highly poUshed. 



Locahty. OfFham chalk-pit, near Lewes. 



ICHTHYOLITES, OR THE FOSSIL llEMAINS OF FISHES. 



The remains of fishes are of far less frequent occurrence in a fossil 

 state, than those of many other tribes of animals ; nor will tliis circum- 

 stance appear extraordinary, when it is considered that the softness of 

 their structure renders them hable to undergo putrefaction with great 

 rapidity, and that such as die a natural death, rise to the surface of the 

 water, and immediately become the prey of a mrdtitude of assailants. A 

 concurrence of circumstances, by which the destruction and envelopement 

 of these animals m aybe instantaneously effected, seems therefore necessary 

 to the preservation of their remains in the mineral kingdom. Hence 

 some naturalists have asserted, that wherever petrified fishes occur in 

 considerable numbers, it may be inferred that they perished by some 

 sudden catastrophe which destroyed and overwhelmed them in shoals, in 

 the very spots where they are now found entombed*. 



The Rev. Graydon f, in an interesting memoir on the fossil fish 



of Monte Bolca, endeavours to account for the phenomena they exhibit, 

 by a very ingenious theory, that appears to be in perfect accordance with 

 the facts already known on this subject. He supposes that the fishes 

 were destroyed by submarine volcanic eruptions, by which immense 

 masses of calcareous stone were ejected in a calcined state ; and which in- 

 volving the animals, &c. within its reach, subsequently became consolidated, 

 and now forms the cream-coloured matrix of these celebrated fossils. 



The minerahzed remains of fishes occur in various parts of England ; 



* Rees' Cyclopce<Ua, Art. Ichthyolites. Diet. D'llist. Nat. Tome viii. p. 550. Martin's Syst. 

 Arrangement, p. 29. 



f Irish Transactions, Vol. v. p. 310. 



