389 
None of theso characteristics, liowever, are coiistant. As to 
the longitudinal folds we find numerous forms intermediate between 
those with well developed folds and tliose quite without folds. Siicli 
connecting links have often heen figured and sometimes classed 
among groenlandicum, sometimes among undatum. (See for ex- 
ample G. O. Sars: Mollusca regionis arcticæ Norwegiæ PI. 25, Fig. 
1, and PI. 24, Fig. 3.) The second and third distinguishing marks 
are, according to Friele’s investigations, tolerably constant, although 
Friele himself remarks that the forms pass into one another ^). 
Friele records the variation of the number of denticles for the 
two forms as follows: 
A. Buccinum undatum, from Hammerfest, Norway, 26 speci- 
mens examined: 
8 specimens 
12 
2 
1 
1 
1 
1 
11 
11 
4—5—4 
4—6—4 
4—7—4 
4—9—4 
3—6—4 
3— 7—4 
4— 8—5 
B. Buccinum groe^ilandicum, from Hammerfest, Norway. 65 
typical specimens examined (presumably with small longi¬ 
tudinal folds or quite without those): 
5 specimens 3—3 — 3 
42 „ 3-4-3 
12 „ 3—5—3 
1 
1 
2 
2 
11 
11 
11 
11 
3-6—3 
3— 3—4 
4— 4—3 
4—5—3 
B H. Friele; „Ueber die Variationen der Zahnstructur bei dem Genus 
Biiccinum“. Jahrb, Deustch. Mal. Gesell. 6. Jahrg. 1879. 
