REVIEWS. 



91 



mountains. Long lines of Osars (or heaps of detrital matter) 

 were found accompanying the erratic blocks, and their pre- 

 valent direction was from N.N.E. to S.S.W. 



REVIEWS. 



Description des coquilles fossiles de la fa7nille des Rudistes, 

 qui se trouvent dans le terrain cretace des Cor bier es ; par 

 Oscar Holland du Roqiian. Carcassonne, 1841. 4to. 

 ivith plates. 



During the last few years of the present era of geological 

 discovery, great zeal and talent have been displayed in the 

 examination of peculiar tribes of extinct animals, with a 

 view to trace their identity or affinity with recent produc- 

 tions possessing apparently a similar external appearance 

 and construction. Amongst the most striking of these pro- 

 ductions, and at the same time those which have been the 

 most imperfectly understood are the lower orders of Mol- 

 lusks so common in the older secondary strata of the earth's 

 crust, and it is therefore a source of pleasureable duty to 

 contemplate the supervision of any work relating to a sub- 

 ject, possessing so much novelty, and so many attractions. 

 The work before us embraces one of the groups and contains 

 an elaborate account of the distribution of the species in the 

 district of Corbieres in the department of Aude. 



The fossils of which the family of " Rudista^' is composed, 

 are confined to the cretaceous system : the lower strata does 

 not contain any organic production in any way resembling 

 them, and they seem to have entirely disappeared at the 

 period of the deposition of the most recent secondary or old- 

 est tertiary rocks. In addition, a particular geographic 

 distribution is assigned to these fossils in the district of 

 Corbieres ; for although the chalk formation of central Eu- 

 rope contains abundance of them, they are so rare in the 



