The Staircase Shells. Ladder Shells. Wentletraps 



S. Indiorum, Cpr., is found on the California coast and nortii 

 to Vancouver Island. It is thin and white, an inch long, with 

 numerous cross ribs on its ten whorls. Occasionally it is found 

 in a variety, iinda, tinged brownish purple, in Southern Califor- 

 nia. 



S. mirifica, a rare deep water species, I mention here because 

 it is unique. It has the distinction of being the most highly 

 coloured of all deep sea mollusks. As a rule abyssmal shells 

 are dull and colourless. This notable exception is white, tinted 

 with bright rose-colour. 



159 



