372 PEOCEEDINGS OP THE GEOLOaiCAL SOCIETY. [JuilO 4, 



The Nelumbium and the "Water-lily demand the presence of fresh 

 water and exclude any idea of salt water ; therefore one can easily 

 explain the appearance of Pdludina, Cydas, Unio, and Planorhis at 

 this place. Accordingly we admit the existence of a freshwater lake 

 there, the "Water-lilies and Lotos spreading their leaves over its 

 waters, and the Sequoias, the Palms, and the Andromedas surround- 

 ing its banks. 



The lake could not have been far from the sea, nor much above it, 

 because these freshwater formations alternate with those of brackish 

 water, — a circumstance which shows that the sea broke in at times, , 

 and changed the fresh water into brackish, and finally into salt water j 

 so that the plants confirm the conclusions formed by Prof. Forbes from 

 the animals. 



The exact sections in Porbes's memoir give us very interesting 

 indications of these events ; and perhaps it may be possible, by a 

 careful study of the plants these beds contain, to arrive at conclu- 

 sions not only respecting the change of the freshwater and brackish 

 formations, but also as to the seasons in which they took place. 

 The <* Black Band" forms the basal stratum of the Hempstead 

 series ; and the next succeeding stratum shows us that already, in 

 the beginning of the formation, a lake of fresh water existed there ; 

 for it is particularly in this portion of the deposit that rhizomes and 

 leaves of Nelumbium are found, and with them the freshwater shells. 

 An influx of salt water seems to have taken place before the forma- 

 tion of the " WTiite Band," as here there occur some brackish- water 

 shells. During the formation of the "middle freshwater marl" of 

 Forbes (op. cit. p. 42), the freshwater conditions were predominant, 

 and the Water-lilies appear represented by a quantity of seeds, with 

 Unio and Pdludina. The '^ upper freshwater and estuary marls "of 

 Forbes are nearly always a freshwater formation; and we only 

 get a true marine stratum in the '' upper Corbula-bed." It seems, 

 therefore, that from the beginning to the end of the Hempstead 

 Series there was a lake which received fresh Water from a river, but 

 that from time to time it was supplied with salt water, which at last 

 became predominant, by which the freshwater population was sup* 

 planted by an exclusively marine one. 



To these general remarks I add the following observations on the 



1. Sequoia Cotjttsi^, Heer. PI. XVIII. figs. 1-7. 



Eeer, Fossil Flora of Bovey Tracey, Phil. Trans., pis. 8, 9, 10. 



Host of the specimens are from a bed 7 feet above the " Black 

 Band " of Forbes ; but one specimen was found about 2 feet 6 inches 

 from the top of the " second division " of Forbes (op. cit. p. 41). 



This species wholly agrees with that of Bovey Tracey. It has 

 thin twigs (figs. 2, 4) which are covered with imbricated leaves. 

 The leaves are alternate, acuminate, and mostly have a somewhat 

 curved point ; they are either pressed against the twigs (fig. 2), or 

 spread in the upper part (fig. 4), Hke the Bovey plant. The cones 

 are also of equal size, and formed by peltate, many-edged scales 



