92 



THE GEOLOGIST. 



northern districts, that with the exception of three or four 

 examples, not a specimen of any species of Rudista has been 

 formed in the chalk formation beyond 47^ — 48^ north latitude. 



M. D'Archiac in a memoir exported in the Bulletins of 

 the Geological Society of France, recounts all the localities 

 in which these fossil remains have been found. " Species of 

 this family have been found in the environs of Lisbon (Por- 

 tugal), in the south of Spain, in the strata of the Pyrenees, 

 and the prolongation of that range in the Asturias. Their 

 abundance in the south-west of France is well known, and 

 they are again traced at Corbieres (at the foot of the eastern 

 Pyrenees), then in the departments of Gard, Vaucluse, 

 Bouches du Rhone and Var, in the province of Milan, in 

 the neighbourhood of Verona, in the Tyrol, Salzburg, Styria 

 and generally in the eastern Alps ; in Illyria, Transylvania, 

 the Carpathian chain, Dalmatia, Albania and the Morea.'^ 

 Mr. C. Prevost notices their occurrence in the chalk of 

 Mount Erix in Sicily, and further east, they are again found 

 in Asia Minor, at Lebanon and Mount Sinai. This proves, 

 as has been mentioned, their particular distribution ; and, if 

 an isolated Hippurite has been found in England, a Spheru- 

 lite at Maestricht, and another at Brighton, their occurrence 

 is so rare that sufficient proof is thereby afforded that these 

 animals could not have Jived and multiplied in these parts. 



But again, Mr. Roquan observes, as their distribution is 

 peculiar to the cretaceous formation of central Europe some 

 particular cause must have existed to produce this result, 

 and it remains for us to trace the reasons. 



Thus, as an example, we first find a number of species at 

 present abundant in the Mediterranean, whilst they are abso- 

 lutely unknown in the ocean, although the conditions of the 

 two localities are found to be the same, such as temperature, 

 &c. It is evident, therefore, although the strata differ in 

 paleontological aspect, that the lithological character of the 



