316 American Seashells 



lated with browns and yellows. Strap-like, brown hairs not numerous. In- 

 terior of valves greenish white to white. Moderately common. 



Mopalia hindsi Reeve Hinds' Mopalia 



Alaska to the Gulf of California. 



2 to 3 inches in length, oblong, flattened and resembhng M. ciliata 

 Sowerby, but generally smoother. Girdle brown, rather thin and fairly 

 wide, and almost naked except for a few short hairs. Interior of valves 

 white with short crimson rays under the beaks. Moderately common. 



Genus Placiphorella Dall 1878 

 Placiphorella velata Pilsbry Veiled Pacific Chiton 



Figure 66a 



Monterey, California, to Lower California. 



1 to 2 inches in length, readily recognized by its flat, oval shape and 

 wide girdle which is very broad in front. There are a few hairs on the 

 girdle which, if viewed under a lens, will be seen to be covered by a coat 

 of diamond-shaped scales. Girdle reddish yellow. Valves colored a dull 

 olivaceous brown with streaks of buff, blue, pink or chestnut. Interior 

 of valves white with a slight bluish tint. Posterior valve with i to 2 slits 

 and with very large sutural plates. Fairly common intertidally. 



Genus Katharina Gray 1847 

 Katharina tunicata Wood Black Katy Chiton 



Figure 66b 



Aleutian Islands to southern California. 



2 to 3 inches in length, oblong and elevated. Characterized by its shiny, 

 naked, black girdle which covers % of each gray valve. Valves usually 

 eroded. Anterior valve densely punctate. Interior of valves white. Foot 

 salmon to reddish. Very common between tides, especially in the north. 



Genus Syimnetrogephyriis Middendorff 1847 

 (Amicula Gray 1847, not 1842) 



Symmetrogephyrus vestitus Broderip and Sowerby Concealed Arctic Chiton 



Figure 66c 



Arctic Seas to Massachusetts Bay. Arctic Seas to the Aleutian Islands. 



I to 2 inches in length, oval, rather elevated. Valves covered with a 

 thin, smooth, brown girdle except for a small, heart-shaped exposure at the 



