THE BEXTHAL 



187 



The starfish Astropecten eats small worms, echinoderms, and mollusks. 

 The snail Natica (Fig. 27) moves about 2 to 5 cm. below the surface 

 of the sand and attacks mollusks, boring through their shells, and 

 sucking out their contents by means of its proboscis. 



Fig. 25.— Haploops tubicola. Enlarged five times. After Delia Valle. 



Some fishes also hide themselves by burying wholly or partly in the 

 sand, and thus lie in wait for their prey. All these have a flattened, 

 light-colored ventral side, eyes usually directed upward, and the mouth 

 also often turned up. While in free-swimming carnivorous fishes the 



Fig. 26. — Amphioxus, Branchiostoma 

 lanceolatum, burrowed into the sand. Slightly 

 enlarged. 



Fig. 27. — Natica josephina attacking a bi- 

 valve in sand, holding its prey with the di- 

 visions of its foot while boring through the 

 shell. After Schiemenz. 



Fig. 27 



eyes are only slightly movable, with their fields of vision overlapping 

 only a little (10-30°), the eyes of the flatfishes and of other bottom 

 dwellers are very mobile and their fields of view overlap to the extent 

 of 35-80°, according to the species. This binocular vision probably 



