391 
It looks as if the iiumber of denticles is swinging rouud two 
different types as centres, viz. 4—6—4 and 3—6—3. As a rule 
the forms witli the smallest longitudinal folds have the smallest 
numher of denticles, still it is not always the case. 
Fig. I, II, III. Buccinuni undatum L. Eeykjavik. 
Fig. IV, V. Buccinum undatum planum Verkr. Eeykjavik. 
Fig. VI. Buccinum undatum groenlandicum Chemn. Stykkisholm. 
It may further be added that C oli i n^) has examined nume- 
rous radulæ of Buccinum undatum from Denmark, and among these 
he has found formulæ as follows: 
3—7—5 3—4—6 
3—5—5 4—4—4 
3—5—2 4—3—5 
In several of these cases, however, if not in all, the radulæ 
have been misshapen. 
Jonas Collin: „Om Lim^ordens marine Fauna“. Kjøbenhavn. 1884. 
