220 HALF AN HOUR WITH SHELL-FISH (BIVALVES). 



In the Psammobias this style of ornamentation is so 

 characteristic and beautiful, that Mr. Wood has 

 called them "Sunset-shells," in allusion to the 

 broadening rays of coloured light which are seen 

 during a fine sunset. In them the rays are pink on 



Fig. 121. 



Fig. 122. 



'a arenanct. 



Mya truncata. 



a yellow or red ground. They are obtained alive 

 only by dredging, although one species is often 

 found ashore, called tellinella. 

 The " Sand-mussel " (Mya arenaria) has already 



