389 
None of these characteristics, however, are constant. As to 
the longitudinal folds we find numerous forms intermediate between 
those with well developed folds and those quite without folds. Such 
connecting links have often been figured and sometimes classed 
among groenlandicum, sometimes among undatum. (See for ex- 
ample G. O. Sars: Mollusca regionis arctice Norwegiæ Pl. 25, Fig. 
1, and Pl. 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 thé vaåriåtion of the number of denticles for the 
two forms as follows: 
A. Buccinum undatum, from Hammerfest, Norway, 26 speci- 
mens examined : 
8 specimens 4—5—4 
05 1 ERR 
1 3 RARE 
1 3 6—4 
FF Sd 
1 FERSE 
B. Buccinum groenlandicum, from Hammerfest, Norway. 65 
typical specimens examined (presumably with small longi- 
tudinal folds or quite without those): 
5 specimens 3—3—3 
1: 55 187068 
Le 4 2 8084 
2:55, 5484-68 
2 år-5—8 
7) H, Friele: ,,Ueber die Variationen der Zahnstructur bei dem Genus 
Buccinum"". Jahrb. Deustch. Mal. Gesell. 6. Jabrg. 1879. 
