224? Geological Society, 



aquatic species of the genera Limnea, Paludina and Planorbis. This 

 large proportion of land shells is very general in the formation. 

 The author then made a collection of such shells as are now drifted 

 down by the Rhine and occasionally cast ashore by the waves, in 

 which case the shells for the most part retain their colour and are 

 perfectly distinguishable from fossils washed out of the loess. Out 

 of two hundred and seventy -three individuals thus procured, one 

 hundred and forty-seven were land shells and one hundred and 

 twenty-six aquatic. The author infers that if the waters of the 

 Rhine were now received into a lake, the sediment of such a lake 

 might contain more terrestrial than aquatic shells. 



After some observations on the hollows and furrows in the gravel 

 of the Rhine which have been filled with loess, the author states 

 that the interior of the crater of the volcanic mountain called the 

 Roderberg is in great part filled up with pure loess, which was 

 pierced to the depth of 65 feet in digging a well in 1833. But 

 although this and other sections prove the posteriority of the loess 

 in general to the volcanic formations of the Eifel, Mr. Lyell ad- 

 mits that at Andernach there have been considerable falls of pumice, 

 scoriae and volcanic sand during the period of the formation of the 

 loess. In proof of this, the sections in the Kirchweg near Ander- 

 nach, are described. 



The loess is then stated to be spread almost everywhere over the 

 tertiary and secondary strata around Mayence, Oppenheim, Alzey, 

 Flonheim, Eppelsheim and Worms. There is a section of loess 

 with shells, alternating several times with gravel, at the Manheim 

 gate of Heidelberg. 



The loess between Heidelberg and Heilbronn appears to attain 

 the height of seven or eight hundred feet above the sea. In this 

 district, shells of the Succinea elongata alone are so abundant as to 

 exceed in number all the accompanying land shells. The author 

 then mentions the loess near Stuttgard and between Goppingen and 

 Boll in Wurtemberg. He found no traces of it in the course of a 

 tour by Heidenheim, Solenhofen, Nuremberg, Bayreuth, and the 

 cave district of Muggendorf, but he found it again between Bam- 

 berg and Wurtzberg in the valley of the Mayne. It was wanting 

 in the Spessart and the country around Aschaffenberg, but is abun- 

 dant near Frankfort and in several parts of Nassau. In the valley of 

 the Lahn near Limburg, it contains its usual shells and alternates 

 frequently with gravel. 



From these facts and others mentioned in the paper, the author 

 deduces the following conclusions: — 



First, That the loess is of the same mineral nature as the yellow 

 calcareous sediment with which the waters of the Rhine are now 

 commonly charged. 



Secondly, The fossil shells contained in the loess are all of recent 

 species, consisting partly of land and partly of freshwater shells. 



Thirdly, The number of individuals belonging to land species 

 usually predominates greatly over the aquatic, and this seems now 

 to be the case with the modern shells drifted down by the Rhine. 



