Note on the Damsli species of Pisidium. 
By 
A, C. Johansen . 
The nevv great and most valuable work by B. B. Woodward: 
Catalogue of the British species of Pisidium (London 
1913) wili without doubt influence the determination of the Pisi- 
diurns in many other countries tban 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 
steenbuchii. 
The little shell which Woodward mentions as Pisidium 
parvulum is a very distinet and characteristic form, but I think 
it more safe to name it P. parvulum B. B. Woodward than P. 
parvulum Cl es s in. 
This little form has under the umbones one or two well 
marked ridges which are running parallel with the growth lines 
and are 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 
growth 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. (3 
