some New Points in British Geology. 267 



West Cowes there are several fine sections along the shore. 

 The total thickness of unclassified strata in the Isle of Wight 

 is four hundred feet, if not more, and within this range are 

 at least two distinct sets of organic remains. The fluvio- 

 marine beds in all, including the Headon series, are very 

 nearly six-hundred feet thick. 



On the question whether Temperature determines the distri- 

 bution of Marine Species of Animals in depth. By James 

 D. Dana, Esq. 



It is a question of much interest, how far temperature in- 

 fluences the range of zoological species in depth. From a 

 survey of the facts relating to coral zoophytes, the author ar- 

 rived at the conclusion that this cause is of but secondary 

 importance.* After determining the limiting temperature 

 bounding the coral-reef seas, and ascertaining the distribution 

 of reefs, it was easy to compare this temperature with that 

 of the greatest depths at which the proper reef corals occur. 

 This depth is about 100 feet, now the limiting temperature, 

 68°, is reached under the equator at a depth of 500 feet, and 

 under the parallel of 10° at a depth of at least 300 feet. 

 There must therefore be some other cause besides tempera- 

 ture ; and this may be amount of pressure, of light, or atmo- 

 spheric air dissolved in the waters. 



Professor Forbes has remarked that the deep sea species 

 in the iEgeanh ave a boreal character ;t and Lieut. Spratt has 

 ascertained the temperature at different depths, J and shewn 

 that the deep-sea species are those which have the widest 

 range of distribution, most of them occurring north about the 

 British shores, or north of France. Yet is it true, that the 

 species which occur in deep water in the iEgean are found in 

 shallow waters of like temperature about the more northern 

 coasts ? If so, Lieut. Spratt' s conclusion, that temperature 

 is the principal influence which governs the distribution 



* Exped. Report on Zoophytes, 1846, p. 103 ; and on Geology, p. 97 ; this 

 tour, xii, 180. 



t Report on the iEgean Invertehrata, Rep. Brit. Assoc. 1843, p. 130. 

 X Rep. Brit. Assoc. 1848, p. 81. 



