388 
crispdita L., is, accordiug to Mørch^), recorded by Olafseii from the 
tract between tide-marks at Faxefjordr. 
Systematical remarks. 
With regard to Dendronotus arborescens it must be noted 
tliat on a specimen which I examined the number of lateral teetb 
was very small, viz. 7, on each side. This is, as far as I know, 
the smallest number which hitherto has been observed in that 
species. K. Bergh^) records the range of variation of the 
number of denticles on each side from 14 to 21, and Posselt^) 
extends it to 9—25. 
As to the systematical relation of Littorina arctica, Møller, 
I have in a previous paper^) drawn the attention to the forms 
intermediate between this and Littorina ohtusata L. 
Eespecting the systematical relation of Buccinum groenlandi- 
cum, Chemnitz {B. cyaneum, Bruguiére) I must maintain that its 
range of variation is in contact with that of Buccinum undatum, 
L. The distinguishing marks between these two forms may be 
drawn up as follows: 
Buccinum groenlandicum 
1) Longitudinal folds on the shell 
wanting, or very short. 
2) Number of denticles on late¬ 
ral plates 3. 
3) Number of denticles on all 
three teeth at most 12. 
Buccinum undatum 
1) Longitudinal folds on the shell 
well developed. 
2) Number of denticles on late¬ 
ral plates 4. 
3) Number of denticles on all 
three teeth at least 13. 
O. A. L. Mørch; „Faunula Molluscorum Islandiæ“. Vid. Medd. Na- 
turh. Foren, Kjøbenhavn. 1868. 
K. Bergh: Die Nudibranchiaten. Gesammelt wahrend der 
Fahrten des „Villem Barents“ etc. Bijdragen tot de Dierkunde. 
Amsterdam 1886. 
H. Posselt: „Grønlands Brachiopoder og Bløddyr“. Meddelelser om 
Grønland. 23. Hefte. Kjøbenhavn 1899. 
A. C. .Johansen; „On the variations observable in some Northern 
species of Littorina“. Vid. Medd. Naturh. Foren. Kjøbenhavn 190L 
