82 
came from Ronneby, Sweden, belonged to P. obtusale, I have some 
doubt as to whether the original specimens of Clessin's parvulum 
belong to that characteristic form which Woodward and I myself 
have mentioned under that name. 
Pisidium parvulum B. B. Woodward is the smallest Pisidium 
found in Denmark and the smallest one dealt with in Woodward's 
Monograph. It has some resemblance with young ones of P. supinum 
A. Schmidt, but its outline is more squarish. By the ridges 
mentioned above and by its characteristic hinge (figured by Wood- 
ard) it differs essentially from all other Danish and Scandinavian, 
Pisidiums. 
w  P. parvulum B. B. Woodward was found by me in the Danish 
lake Fursøen in 1898 and mentioned in my paper ,; Bidrag til 
vore Ferskvandsmolluskers Biologi" (Vid. Medd. Naturh. Foren. 
Kjøbenhavn 1899) as P. parvulum Clessin. 
It has been found later on by H. Lynge, in Ladegaardsaa 
Damhussø and Farum Sø, Sealand, and by Teilman-Friis 
in Hastrup Sø in West Jutland, and Woodward records 
it now from Lake Baikal. 
A peculiar triangular thick-shelled  Pisidium was found 
some years ago in Sjæl Sø, Sealand, by H. Lynge and was 
determined by Westerlund as Pisidium supinum A. Schmidt. 
I found later on a corresponding form in the Fursø, Sealand, and 
in Grenaa Aa, Jutland, and following Westerlund I referred 
all these to P. supinum Schmidt. Woodward has now referred this 
form to P. casertanum as a variety, and I must admit that he is right. 
From this it follows that the real P. supinum A. Schmidt is DOW 
only known. from one locality in Denmark, viz. from Skarritsø, 
Sealand, where H. Lynge has found a few specimens. 
In Denmark we have the following species of Pisidium: 
Pisidium amnicum, Miller: in all parts of the country 
— … astartoides, Sandberger; only from the Pleistocene: 
land, Funen 
Sea- 
