146 Shell Life 



teeth is shown in this figure of a right valve ; in 

 the left valve the hinder cardinal is much smaller 

 and not cleft. The beaks are turned slightly to 

 the hinder end of the shell. 



The Tellin-like Sunset-shell (P. tellinella) is thin, 

 glossy, yellowish white, marked with fine concentric 

 ribs, the grooves as well as the ribs being polished, 

 and the radiating bands are of 

 pink, red, or violet. A streak of 

 crimson usually runs along the 

 upper edge of the valves before 

 , _ , ^ ,, and behind the beaks. The in- 



ike Sunset-shell 



terior is highly polished, with 

 the external colouring repeated. The animal is 

 white, its mantle with a tooth-like fringe, and the 

 upper (excurrent) siphon is marked by fine lines of 

 white from end to end. This brilliant little mollusk 

 occurs locally all round our coasts, burrowing in 

 sand between 4 and 85 fathoms, and occasionally 

 swimming after the manner of the Pectens by 

 flapping its valves. 



The Ribbed Sunset-shell (P. costidata) differs from 

 the last chiefly in the character of the posterior 

 slope of the shell, which bears from 12 to 20 slight 

 but sharp ribs running from the beak to the hinder 

 margin, which is notched in consequence. In addition 

 the shell is thinner, the valves unequal, and the less 

 regular rays are of deeper tints. The animal is 

 white tinged with pink, tlie mantle edges thickened 

 and slightly fringed. This is more local than the 

 last, and can only be obtained by dredging, as its 

 habitat is in fine sand in from 15 to 85 fathoms 

 of water. It is slightly more than 1 inch in length. 



