296 
The first named character can not be relied on. I have exa- 
mined 16 speciraens of L. parva, which Teilman-Friis has kindly 
placed at my disposal, and have forind the nuraber of denticles very 
variable. In the same radula the central tooth may sometimes have 
3 denticles, sometimes 5 or another nurnber. The normal number 
of denticles on the central tooth in these 16 specimens was as follows: 
10 specimens 3 denticles (Fig. 1 a). 
2 — 3 or 5 — 
3 — 5 — 
In one case the number was so variable that I could not de- 
cide which was the normal one. It varied on the different teeth 
from 3 to 8. A central tooth with 8 denticles is shown in Fig. 2. 
d 
Fig. 1. Teeth of IAttorina parva Mørch from Limfjorden (presumed to be 
a dwarfed form of Littorina littorea Linné). 
a Central tooth, b, c, d first, second and third lateral teeth. 160 /i- 
Fig. 2. Central 
tooth o f L. par¬ 
va from Skive- 
fjord, Denmark. 
160 / 
/ 1 • 
The second character is also far from being a per¬ 
sistant one. To Teilman-Friis’s valuable tables I 
can add the following measurements of shell and ra¬ 
dula of 10 specimens of L. parva from Skivefjord, 
and 10 specimens of L. littorea from Frederiks¬ 
havn : 
