Fig. 123. 



Tapes aurea. 

 Fig. 124. 



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



sculpture the surface (Fig. 123). One species, abun- 

 dant in our seas, decussata, has these lines deeper 

 than the rest, cut into the shell much after the way in 

 which a flat file is cut in opposite 

 crossing lines. In the species jmZ- 

 lastra (Fig. 124) the sculpturing 

 is much more delicate and finer, 

 and the shells smaller. A hand- 

 some and not uncommon shell 

 is the Venus, one species of which 

 ( Venus fasciata) is nearly trian- 

 gular in outline, with a gently 

 rounded base. All the way up 

 to the beak there run a series of 

 strong concentric ribs, so that 

 it is a species not difficult to 

 determine. Its colour is generally brownish, diver- 

 sified agreeably with purplish bands running down 

 and crossing the ribs aforesaid. The foot is white, 

 and the animal possesses two tubes or siphons for 

 breathing water in and out. There are several species 

 living in our seas, all of which are pretty objects. 

 In one ( Venus verrucosa) the surface of the valves is 

 covered with deep furrows. Cytherea chione is a hand- 

 some mollusc allied to the latter, which lives in deep 

 water, especially off the southern coasts. Its colour 

 is chestnut-brown, having bands of paler hue 

 radiating from the beak. Artemis exoleta is another 

 related bivalve, whose large, thick, solid shells are 

 beautifully ornamented with bands of pink and light 



Tapes pullastra. 



