SHERES WILHOUL CANALS 217 
instead of being nearly smooth, as in the last two 
species, is marked by a good number of more or 
less developed spiral ridges. 
Its color varies from white 
to black, but it is usually of 
a yellowish brown. 
Littorina aleutica, Dall, the 
Aleutian Littorine, Figure 
234, is found in the far north, 
as its name indicates. The 
broad pillar of the shell is 
white, the aperture dark, 
while the outside of the shell 
is yellowish brown. The di- 
ameter is about twelve milli- 
Fig. 234, x 3 (*) meters. 
Another shell from the 
same locality is shown in 
Figure 235. It is named Lit- 
torina atkana, Dall, the Atka 
Littorine. It is a large shell, 
20mm. high, and its surface 
is nearly smooth. Most speci- 
mens arechestnut brown 
throughout, but some have 
bands, as shown in the figure. 
The pillar, or columella, is 
broad and white. 
Fig. 235, x 7 
Closely allied with the Littorines are the 
little Chink-shells, the very minute picture 
of one of them being shown in Figure 236. 
Fig. 23 
° Tts name is Lacuna unifasciata, Cpr., the 
