Note on the Danish species of Pisidium. 
By 
A. C. Johansen. 
Tue new great and most valuable work by B. B. Woodward: 
Catalogue of the British species of Pisidium (London 
1913) will without doubt influence the determination of the Pisi- 
diums in many other countries than Great Britain. This will 
Certainly be the case here in Denmark, although the determinations 
at our Zoological Museum of Copenhagen are mostly in agreement 
With those of B. B. Woodward. 
It is interesting and satisfactory to note that Woodward has 
placed Clessin's fossarinum and rivulare as synonyms to Poli's 
old species casertanum. It is undoubtedly also with good reason 
that Clessin's globulare is placed as a synonym to Møller's 
steenbuchti. 
The little shell which Woodward mentions as Pisidium 
Påarvulum is a very distinct and characteristic form, but I think 
it more safe to name it P. parvulum B. B. Woodward than P. 
Parvulum Clessin. 
This little form has under the umbones one or two well 
marked ridges which are running parallel with the growth lines 
and åre most conspicuous in the middle of the shell. They re- 
Semble the appendiculæ on the umbones of P. supinum and P. 
henslowanum, but those appendiculæ are not parallel with the 
B8Towth lines. This very characteristic feature is not mentioned by 
Clessin in his description of parvulum, and as some ,,co-types' 
of P. parvulum Cl., which were determined by Westerlund and 
Vidensk, Meddel. fra Dansk naturh. Foren. Bd. 66. 6 
