260 WEST AMERICAN SHELLS 
Fissuridea murina, (Cpr.) Dall, the White Key- 
hole-limpet, (Glyphis densiclathrata). This species 
has a much smaller and more delicate shell than 
the last. It is oblong in shape, with curved ends. 
The roundish oval hole is one-third of the shell’s 
length from one extremity, and there are numerous 
fine ribs, checked by concentric ridges. The color 
is pure white, at least in dead specimens, and the 
length is about 15mm., a little less than the diame- 
ter of a silver dime. 
Lucapina cren- 
ulata, Sby., the 
Great Keyhole- 
limpet, Figure 
s 293... ‘his is, by 
Z = + far the largest 
‘ * and finest of the 
American Fissu- 
rélide. A small 
meee figure of the shell 
is shown in Figure 293. Though this shell is often 
some four inches long, the animal is much larger, 
and somewhat resembles a brick both in shape and 
size. It has a huge yellow foot and a black mantle, 
which nearly conceals the white shell which rests 
upon the animal’s back. 
This shell is marked by many radiating ribs and 
concentric lines of growth; it has a large, oblong 
hole to one side of the center, around which, inter- 
nally, is a thick rim of enamel. The crenulated 
or scalloped edge of the shell is a marked feature, 
and suggested its name. Internally the shell is of 
a pure, glossy white, but the outside is somewhat 
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