OF THE-XEVEL OF THE SEA. 71 



ded in a finely laminated clay belonging to it, and which 

 we observed in a section formed by a stream, passing from 

 under the sea to a higher level ; it abounded in marine 

 shells, of which we distinguished twenty-four species, not 

 more than one-half of which have been found in the adjoin- 

 ing inlet, and one-third of them are altogether unknown as 

 British. A proportion so great I considered as altogether 

 accidental, but having since examined a locality in which it 

 was equally large, T attribute it in part to the circum- 

 stance of both these deposits being sea bottoms and not 

 beaches, and consequently being in a great measure des- 

 titute of the common littoral shells which abound in them, 

 but chiefly to the fact that the extinct or unknown spe- 

 cies are those which occur in greatest abundance in the 

 raised beds. 



A flood in the stream had washed numbers of the fossil 

 shells out of the clay, and left them on the shore mixed up 

 with recent ones ; a conchologist unaware of their origin 

 must have been delighted with his success in discovering a 

 locality which afforded so many new species.* 



Amongst them Mr Sowerby found a panopcea which 

 was new to him, but which he has since identified with the 

 P. Bivonce, from the elevated clay beds near Palermo. It 

 is described and figured by Dr Philippi in the " Enumera- 

 te Molluscorum Siciliae." (Tab. II. Fig. 1.) Mr Wood 

 has also pointed out to me one from the crag which is ap- 

 parently of the same species. 



* This mixture of shells from deposits of different ages has heen ad- 

 duced hy Mr Charlesworth as one of the sources of error in the infer- 

 ences drawn from the per-centage of living and extinct species in the 

 tertiary formations. It is no doubt a possibility which ought always 

 to be kept in mind ; but it cannot affect the present inquiry, except in 

 the rare cases of shells which are actually extinct having been sup- 

 posed to be recent species. Marine shells in situ in elevated beds 

 must necessarily belong to the period when the sea stood at a higher 

 leveL 



