60 
CALIFORNIA SEA-SHELLS. 
file is absent, leaving the foot exposed, and in a 
good condition for pressing against the side of 
the burrow. In time, the shell forms a rounded 
end, probably after most of the hard work of bor- 
ing: has been accomplished, and the animal has 
a secure home. This species has curious uin- 
bonal reflexions, which adhere closely to the 
shell. They do not work to no purpose, for 
thousands of them are now engaged in filing 
away dangerous reefs, along the coast. 
Zirphcea crisp ata, Linn., Rough Piddock, Fig. 
4, PI. XVI, is a widely distributed species. It 
bores in the hardest blue clay by means of its 
sharp, rasp-like teeth, which are ranged in rows 
on the forward part of the shell. Within the 
umbo is a curious, spoon-shaped plate or tooth. 
A little supplemental plate covers the hinge area. 
The shell is white, thin and brittle, and it gapes 
widely at both ends ; its common length is two 
or three inches. 
The last species which we will mention is the 
Great California Piddock, Parajpholas Calif or- 
nica , Oonr., shown in Fig. 5, PJ. XVI. This 
noble species is some three or four inches in 
length. The anterior portion is rounded and 
full, while the posterior parts taper to small di- 
mensions, and end in brown flaps of epidermis, 
which project beyond the shell. The rocky 
dust which the animal excavates is utilized in 
building up a strong, thick, conical chimney, 
which protects the siphons 
TIIE END 
