391 
It looks as if the number of denticles is swinging round two 
different types as centres, viz. 4—6—4 and 3—6—3. As a rule 
the forms with the smallest longitudinal folds have the smallest 
number of denticles, still it is not always the case. 
Ang 
NEKN Nil DEN 
Ned 
Fig. I, II, I. Buccinum undatum L. Reykjavik. 
alrg IV, V. Buceinum undatum planum Verkr. Reykjav 
g. VI. Buccinum undatum groenlandicum Chemn. SE HRALL 
N: 
It may further be added that Collin!) has examined nume- 
rous radulæ of Bueccinum undatum from Denmark, and among these 
he has found formulæ as follows: 
3—7—5 3—4—6 
3—5—5 å—4 —4 
3—5—2 4—3—5 
In several of these cases, however, if not in all, the radulæ 
have been misshapen. 
7) Jonas Collin: ,,Om Limfjordens marine Fauna”. Kjøbenhavn. 1884. 
