PIERCED SHELLS AND CHITONS 



259 



border, which resembles a fringe of stiff moss. The 

 outside of the valves is sculptured, but this fact is 

 often obscured by growths of seaweed or other organ- 

 isms. The interior of the valves is of a bluish-green 

 color, while the outside is dark or grayish. Some 

 years this species is quite common, and good speci- 

 mens may be found in rocky places between tide- 

 marks at the time of lowest water. 



Mopalia hindsii, Sby., Hinds's Chiton, is the next 

 species to be considered. Its shell is much depressed, 

 and the surface is nearly smooth. The girdle has 

 only a few short hairs. The color is olive, while the 

 interior is white, with short crimson rays under the 

 beaks. Its length is two inches. It is found in San 

 Francisco Bay and along the coast of central Cali- 

 fornia. By some of the best authorities this is con- 

 sidered as only a variety 

 of the last species. 



Mopalia lignosa^ Gld., 

 the Woody Chiton, is well 

 shown in Figure 257. This 

 fine species has its dis- 

 tinguishing lines clearly 

 brought out in the figure, 

 which represents a large 

 specimen. The valves are 

 light green in color within, 

 while on the outside they 

 vary from almost white to 

 dark green. They are also 

 marked with narrow 

 brown lines, which slant Fig. 257 



