SURFACE DREDGING ON THE DEE. 97 
the separate valves might have been thought to be different 
species, but on examining them when joined together, as I 
was able to do in this gathering, I found all the named 
varieties on the same filament. In the interior of the 
valves there are some curious hispid bodies which are 
often seen in fossil Diatomaceous earths. These may be 
sporangial. 
Chetoceros boreale, Bailey. Abundant. This is a delicate fila- 
mentous form which varies considerably, and presents 
different appearances at different stages of growth. 
Nitzschia panduriformis, Greg. Rare. A small variety. 
Pleurosigma acuminaitum, W. Sm. This is a salt-water variety 
resembling atfenuatum. 
These are some of the most remarkable forms found in three 
different surface dredgings The words “rare,” “common,” 
“abundant,” apply only to each particular gathering. These 
three dredgings show how rich the Estuary of the Dee is in 
minute forms of life. 
