88 ON THE CHANGE OF THE LEVEL OF THE SEA. 



I have to acknowledge my obligations to several distin- 

 guished conchologists for the valuable assistance they have 

 afforded me, in an investigation in which so much depends 

 on the accurate distinction of species. To Thomas Brown, 

 Esq. I am indebted for the figures and descriptions of 

 Plate I, and to Mr Edward Forbes for those of Plate II. 

 To Mr G. B. Sowerby I have also to express my thanks for 

 the readiness with which he has aided me in my researches ; 

 and to the Rev. Mr Landsborough for full and accurate 

 lists both of the recent and fossil shells of his parish and 

 neighbourhood. 



The second or fossil catalogue contains the names of all 

 the shells hitherto discovered in the newer pliocene depo- 

 sits of Britain, amounting in all to 273 species, of which 

 196 are marine, and 68 land and fresh water ; 23 of the 

 marine shells, and 6 or 7 of the land and fresh water, are 

 not known as British; 15 of the marine shells appear to 

 have become extinct, and 8 have been found recent in the 

 Arctic Seas or northern shores of America. It will be ob- 

 served, that some of them occur in the Crag and in the Sici- 

 lian raised deposits. I have in the preceding paper noticed 

 the inferences to be drawn from these facts. It yet remains 

 to be ascertained, whether the change in the testaceous fauna 

 be as great in other localities as it is in the basin of the 

 Clyde. 



