96 SURFACE DREDGING ON THE DEE. 
The forms I found in the Dee were— 
Peridinium (Ceratium) tripos. 
AB te Susus. 
The rarer forms of Diatoms found in this dredging and not 
mentioned in the previous list are— 
Biddulphia aurita, Breb. Rare. This form I have never found 
abundant in the Dee. 
am radiata, Roper. This is a curious variety, easily 
overlooked, and might be mistaken for a Coscinodiscus. 
Triceratium favus, Ehr. Rare. 
e alternans, Bailey. Rare. 
Eupodiscus Ralfsit, W. Sm. Common. 
Actinoptychus splendens, Ralf. This is a beautiful form and I 
never met with it in the same abundance. 
Toxomidia Gregoriana, Donkin These two forms are often found 
‘5 insignis, Donkin on the tidal mud. 
Pleurosigma Normanii, Norman. 
Melosira Westit, WN. Sm. Rare. 
Podostra maculata, W. Sm. Rare. This form is attached when 
in the growing state. 
Niteschia virgata, Roper. Rare. 
Bacillaria paradoxa, Gmelin, rare. 
Doryphora amphiceros, Kiitz. Common. There are several 
different forms of this species. 
Navicula lyra, Ehr. Rare. 
Fe aspera, Ehr. Rare. 
Amphiprora maxima, Greg. Rare. 
Dictyocha gracilis. Common. This is a doubtful Diatom and 
may be a Radiolarian; if so, it is the only one I have 
found in the Dee. 
On August 24th, I had a surface dredging in the Estuary as 
far as the Point of Ayr. All the forms were Diatomaceous. 
Coscinodiscus concinnus, W. Sm. Common. This is a very 
large form, very delicate and thin, and exceedingly convex, 
so much so that the whole form can never be got into 
focus at once. Mr. HarpMan tells me that this form is 
doubtfully concznnus. It is almost always found associated 
with Bacteriastrum. 
Coscinodiscus ecceniricus, Ehr. Common. 
Bacteriastrum varians, Lauder. Abundant. This form has 
' received many names, and been made into many species. 
If this form had been found only in the disintegrated state, 
