296 
The first named character can not be relied on. I have exa- 
mined 16 specimens of L. parva, which Teilman-Friis has kindly 
placed at my disposal, and have found the number of denticles very 
variable. In the same radula the central tooth may sometimes have 
3 denticles;” sometimes 5' or another number. The normal! number 
of denticles on the central-tooth in these 16 specimens was as follows: 
10 specimens 3 "denticles (Fig. 1a). 
2 og: D .! 
3 — 5 SE 
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. 
ets W 
Fig Teeth of -Littorina parva Mørch from eneret steve to be 
a.dwarfed form of Littorina littorea L 
oa he miele tooth, b, ec, d first, second. and third lateral teeth. ev; 
ME Becond character ig also far from being a per- 
sistånt "one. To Téilman-PFriis's våluable tables I 
can add the following measurements of shell and ra- 
tot rl par: dula' of; 10' specimens' of L. parva from Skivefjord, 
ford, Denmark mg 10 meeen of L. littorea from Frederiks- 
havn: | 
