Ostracoda and ansia of Tidal Rivers. 9 
to exposure and rapidity of current. Our examples were 
taken from beyond low-water mark, just below the ** Duchess's 
— ;" the bottom a rather tenacious mu 
F. River Coquet at Warkworth Hermitage. —At this spot 
the river, though subject to a rise and fall of many feet, has, 
owing to its precipitous banks, always a considerable depth of 
water at low tides. The bottom consists of a hard muddy or 
loamy sand, and must often be much scoured by the floods to 
which the river is subjec 
G. River Wansbeck. di eB taken from near low-water 
mark, in a somewhat strong current, about half a mile from 
the mouth of the river; bottom of fucus-covered stones. Pro- 
bably a more sheltered and muddier spot, which might have 
been found higher up the river, would have yielded a larger 
variety of pean: 
H. River Blyth, at the junction of the Sleek burn, about 
two miles from the sea.—Gatherings taken from below low- 
parle is slow and ¢ em ib E the greater part of its 
course, and for a distance of several miles from its mouth 
exposes at low water a large surface of muddy banks to the air. 
1. River Ouse, Yorkshire. —VFrom muddy sand at low-water 
margin of river, a short distance above Goole, forty-five miles 
from the sea. Though the average rise of ‘the tide at high 
water is twelve feet, the water at low tide is fres 
iver Humber.—A dredging on the Ferrity Sand, three 
miles above Hull (and twenty-three miles from the sea), "where 
the river is about two miles and a half wide, and the depth at 
low water is six feet, and at high water twenty-four feet. The 
Humber, receiving the drainage of a larger extent of country 
than any other river of England, the amount of fresh water 
carried by it to the German Ocean is considerable. The ma- 
terial dredged was a fine reddish sand mixed with vegetable 
remains, 
