BUFFALO SOCIETY OF NATURAL SCIENCES 75 



remarkable distribution of marine remains far up the estuaries is due 

 to the strong tidal current which brings the debis of organisms living 

 along shore in the more open waters. This current rushes up the 

 Severn at the rate of 6 to 12 miles an hour and it distributes the muds 

 and microscopic organic remains as far north as Gloucester and to 

 every estuary opening into the Severn. "On these shores, so remote 

 from their source, some of these organic fragments find a permanent 

 resting place, and thus far inland we discover along a river bank 

 deposits, containing marine remains. But those which stay are few 

 compared to those which are washed away again and carried out to 

 sea, there to be deposited in marine mud-banks, probably not far 

 from their original home" (264, 620). Just a few miles above the 

 points at which the marine organic remains were found, the muds 

 were examined and every sample showed abundant sponge-spicules, 

 but these all proved to be of the fiuviatile species, Spongilla fluvia- 

 tilis, and none of the marine forms were found. This is the fauna of 

 the recent muds, but a section through the older alluvial deposits 

 which have a maximum thickness of 50 feet, shows that conditions 

 have been much the same for a long time, and that there has been a 

 constant alternation of conditions, first marine, then terrestrial, with 

 the formation of peat beds. Wherever the estuarine sands and muds 

 are washed over the peat beds a similar fauna, dominantly marine, 

 though with fresh-water forms intermixed is found. The section is 

 as follows in descending order: 



fa. More sandy zone, 5 to 7 feet 

 lb. More argillaceous zone, with dis- 

 I seminated vegetable matter 7 to 8 



[ feet, 



Upper peat, i to 2 feet, 6 inches. 

 Zone 2. Lower clay 



Lower peat, 1 to 4 feet 

 Zone 3. Sands and mud 



Gravel 



Triassic sandstones 



The deposits in the Severn estuary indicate a gradual subsidence of 

 the land or advance of the sea. Both the upper and lower clay are 

 blue and usually highly fossiliferous. In some sections a few feet 

 will show an abundance of Foraminifera followed by several feet 

 containing vegetal matter. In one section in which no peat was ex- 



