PIERCED SHELLS AND CHITONS 257 



varying in hue from orange to dark red-brown, and 

 it is sometimes blotched with white. The valves 

 are richly sculptured and are very beautiful when 

 examined with a lens. The mantle border is covered 

 with fine rounded scales; the length of the creature 

 is from an inch to an inch and a half. It is essen- 

 tially a northern species, reaching from Sitka to the 

 middle of California. 



Ischnocliiton regularise Cpr., the 

 Regular Chiton, is shown in Figure 254. 

 This is truly a regular structure, for the 

 constant breadth is half the length, and 

 the ends are semicircles. The valves 

 are sharply arched and are marked with 

 very fine sculpturing. By the aid of a 

 lens the border is seen to resemble very Fig. 254 

 fine beadwork. The outside is olive or 

 slaty blue, and the interior is light blue; the length 

 is 35 millimeters. 



Callistocliiton palmulatus^ Cpr., the Palm Chiton, 

 has small, high arched valves, marked with raised 

 sculpturing. The anterior valve has eleven ribs, 

 while the posterior one has seven very strong ones, 

 bifurcated behind. Its color is dark brown, and its 

 length is 1 1 mm. It is found at Monterey and Santa 

 Barbara. The variety mirabilis^ Pils, has the last 

 valve enormously thickened. The interior is bluish 

 white. The variety comes from San Diego. 



Callistochiton^ crassicostatus^ Pilsbry, the Thick- 

 ribbed Chiton, has an elevated, oblong shell, the lus- 

 terless surface of which is green or brown. The front 

 valve has seven very strong ribs; the posterior valve 



