The Slipper Shells. Cup^and-Saucer Limpets 



above and inside. Its range covers the whole Pacific coast of 

 America. 



THE CUP-AND-SAUCER LIMPETS 

 Genus CRUCIBULUM, Schum. 



Shell shield-shaped with funnel-shaped cup inside. 



The Cup-and-saucer Limpet (C. scutellatum, Gray) has 

 a heavy, shield-shaped shell with strong radiating ribs crossed 

 by concentric ridges. The hooked beak is near the centre. The 

 general colour is brown. Inside the shell is of a darker colour 

 and polished. The variation in form, height and markings 

 has led to the erecting of a great many species which have been 

 reduced more recently to the rank of varieties. Young shells 

 differ markedly from adults. Length, 2| inches. 



Habitat. — West coast of South America. 



Var. auriculatum is a flat form, pale brown, usually mottled 

 with very rough radiate ridges. It is the West Indian form. 



Var. tubiferum extends north from Chili to California. 

 Small, close ridges radiate from the apex, certain of them bearing 

 sharp, hollow prickles. 



The Cup-and-saucer Limpet (C. striatum, Say) of our east 

 coast is a small, pale cone with circular base and radiating ridges 

 that form a scalloped border. The beak is hooked and almost 

 overhangs the posterior edge of the shell. The flaring cup is 

 attached by its side. Length, less than i inch. 



Habitat. — Whole Atlantic coast. 



Genus CALYPTRiEA, Lam. 



Shell conical, with central spiral apex; aperture basal, 

 circular; diaphragm spiral, margin twisted, free margin convex. 



The European Cup-and-saucer Limpet (C. Sinensis, 

 Linn.) is well known. Its cone is regular, with a spiral apex 

 and circular base. The cup takes a spiral turn or two, forming 

 a deep umbilicus. The shell is thin and smooth and round, pale 

 yellow, shining inside. Quite often the pebble to which the young 

 mollusk attaches itself is so small that the aperture of the shell 

 reaches the outer limits of its surface before the adult size is 



151 



