QQO 
As will be seen the distinguishing features also with regard 
to the iiumber of denticles are very inconstant. We have here a 
form series of which the outer-forms are so dilferent that it might 
appear as if they belonged to two very well marked species, but 
between which all possible transitions can be brought forth. I con- 
sider the groenlandicum a dwarfed Northern littoral variety of B. 
undatum. 
As an example of a variation in a single specimeu of Bucci- 
num undatum groenlandicum the number of denticles on the plates 
in 20 after one another following series can be drawn up. One of 
the series is represented above (Fig.YI). The small indices indicate 
considerably smaller denticles than the usual ones, as the outside 
ones in Fig. VI. 
Withiii the Northern forms of the Genus Buccinum there has 
hitherto only been pointed out one distinguishing mark which will 
allow an objective division into groups, the one namely, whethor 
the egg-capsules are united or not. All the other hitherto em- 
ployed characteristics from the shell, the operculum, and the radula, 
are passing into one another and the limitation of the species is 
here submitted to the pure subjective judgment. 
30. July 1902. 
I 
