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 t filing 

 away dangerous reefs, along the coast. 



Zirphceacrispata,) 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, Parapholas Calif or- 

 nica, Conr., shown in Fig. 5, PI. 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. 



I 



THE END. 



