76 HALIOTIS. 



Group of H. albicans. 



Shell almost smooth, having obsolete fine spiral stria? ; oval, evenly 

 convex, the two sides equally curved ; not carinated at the row of 

 holes ; cavity of spire large, not concealed ; nacre silvery ; muscle- 

 scar not distinct ; holes very small, about 12 in number not tubular. 



Australia. 



Group of H. cracherodii. 



Shell smooth or with low obsolete coarse spirals ; oval, evenly 

 convex, the two sides equally curved ; not carinated at the row of 

 holes ; cavity of spire minute, concealed or nearly so ; nacre silvery ; 

 muscle-scar generally not distinct ; holes small, numerous, not 

 tubular, outside black. 



California. 



Group of H. corrugata. 



Shell large, rounded-oval, convex, carinated at the row of holes, 

 with coarse spiral cords outside and often obliquely waved or cor- 

 rugated ; nacre brilliant, muscle-scar distinct, rough (except in H. 

 gigantea and assimilis) ; columellar plate wide, sloping inward, nearly 

 concealing the small cavity of the spire. Holes few, tubular, a 

 channel below them. 



W. Coast N. America; Japan. 



Group of H. tuberculata. 



Shell much depressed, long-oval, spirally striated and often with 

 coarse radiating lamella? ; carinated at the holes ; cavity of spire 

 small, close to the posterior margin, but visible ; nacre silvery ; 

 muscle-scar not distinct. Holes slightly raised ; columellar plate 

 flat, rather narrow. 



Japan and Seas of Europe. 



Group of H. stomaticeformis. 



Shell small, oval, often much elevated ; sculptured with spiral 

 cords and radiating folds or lamellae ; more or less carinated at the 

 row of holes ; spire subterminal. Holes five or less, somewhat 

 tubular ; columellar shelf wide above, and flat. 



Japan to Viti Is. and N. Caledonia. 



Group of H. pustulata. 



Shell long-oval, right side generally straightened ; carinated at the 

 row of holes ; surface spirally striated, often pustulated or waved ; 



