THE PIDDOCKS. 



211 



widely distributed, being found also on both sides of 

 the Atlantic. I have dug fine specimens from hard 

 blue clay near Bolinas. The internal organs of the 

 animal as well as its shell are ven' curious and inter- 

 esting. Among them is the hyaline stylet, a slender, 

 transparent cylinder, looking like a piece of glass 

 rod. Its use is not certainly known. Nearly all of 

 the Piddocks are phosphorescent in the dark. 



The great California Piddock, ParapJiolas Califor- 

 nica, Conr., Par-a-fo'-las Cal-i-for'-ni-ca, is represented 

 in Fig. 1 80. The shell of this fine species is rounded 

 in front, where it is marked with fine and delicate 

 sculpturing. The rear end of the 

 shell is tapering, and is mainly 

 composed of large scales of epi- 

 dermis. Near the line of imion of 

 the two valves, both above and 

 below, there are accessory plates, 

 long, straight and smooth. Curi- 

 ous spoons of white shell are seen 

 within the valves, beneath the 

 umbones. The shells are white, 

 rather delicate, and are three or 

 more inches in length. The rocky 

 dust which the animal obtains in 

 the process of excavation he uses in 

 building up a strong, conical chim- 

 Fig. iSo. ney, which protects the siphons. 



Martesia intercalata^ Cpr., Mar-te^-si-a in-terca- 

 la'-ta. This is a very small borer from the southern 

 fauna, which is sometimes found in large shells like 

 that of the Haliotis. Its presence sometimes disturbs 

 the occupant of the shell, especially if its burrow 

 has been carried nearly through the pearly lining. 



