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The occurrence of Polymyxus coronalis is of peculiar interest, 
as it has been hitherto considered as growing exclusively at the 
mouths of the Para and the Amazon. It is not a mere accidental 
form, but is abundant in the deposit in all its numerous variations. 
Several years ago I found one specimen in material from one of 
the Atlantic City wells, but supposed at the time that it might 
have been a waif cast upon the shore. As Polymyxus now 
flourishes only in warmer waters the conclusion must be reached 
that the Delaware River delta formed the deposit under conditions 
quite different from those existing at the present time. It is at 
any rate now extinct along the North Atlantic coast. 
The nomenclature of the following list is based upon DeToni’s 
Sylloge Algarum, except in a few cases. 
Achnanthes Hudsonis Grun. 
A. inflata (Kiitz.) Grun. 
A. subsessilis Ehr. 
Actinocyclus Ehrenbergit Ralfs. 
A, subtilis Greg. 
Actinoptychus heliopelta Grun. forma minor. 
Only one specimen has been noticed. 
A, undulatus Ehr. 
A. vulgaris Schum. 
Amphora ovalis (Bréb.) Kiitz. var. gracilis (Ehr.) V. H. 
Aulacodiscus Argus Ehr. 
Auliscus pruinosus Bail. 
Biddulphia Rhombus Wm. Sm. 
Brebissonia Boecku (Kiitz.) Grun. 
I have noticed this form in material from the Saguenay River, 
Can. 
Campylodiscus echenets Ehr. 
The habitat of this species is usually given as marine or brack- 
ish water. Van Heurck is the only authority, as far as I have 
noticed, who states that it occurs in fresh water. I have found 
several specimens in mud taken from a supply reservoir in Phila- 
delphia, the water of which is drawn from the Schuylkill River. 
Cerataulus laevis Roper. 
Cocconets placentula Ehr. 
Coscinodiscus Argus Ehr. 
C. excentricus Ehr. 
