Life of the Snails 17 



pods. A few species of nerites and periwinkles are known to ascend trees 

 near the seashore, although tree-dwelling is best known among certain tropi- 

 cal land snails. In the tropics, the Tectarius prickly-winkles habitually live 

 in or near splash pools along the rocky coast where spray from the waves and 

 drenching rains are constantly changing the temperature and salinity. When 

 the pools are dry the snails are often able to withstand weeks of hot sun 

 and parched conditions. 



Three kinds of snails in American waters are forever destined to wander 

 at large on the surface of the open ocean. The purple Janthina snails are 

 born, live and, in most instances, die at sea. These pelagic snails live upside 

 down and remain at the surface by means of a small raft of bubbles. Small 

 bubbles of air are entrapped in a special mucus secreted by the animal. This 

 clear fluid congeals upon contact with salt water and air, and it adheres to 

 the foot. The entire float has much the appearance of crumpled cellophane. 

 The female attaches her small eggs to the underside of the float where they 

 are partially shaded from the sun's rays. The Janthinas live off the coasts of 

 our southern states, and during certain seasons they are commonly cast ashore 

 in California, Florida and the Gulf States. Specimens have been blown off 

 their Gulf Stream course and been washed ashore in New England and even 

 the British Isles. 



As is the case with so many other pelagic creatures, the shell surface of 

 Janthina which faces downward (the spire of this upside down shell) is 

 colored a light, milky blue. This is probably a protective coloration which 

 blends with that of the surface of the sea, which to an underwater observer 

 is similarly colored. For some unknown reason Janthinas are completely 

 blind. 



Two other groups of gastropods live at the surface of the ocean and, 

 like Jantlmia, live an upside down existence. These are the tiny brown 

 Litiopa snails which adhere to floating sargassum seaweed by means of a 

 silken thread of mucus, and the heteropods or fin-footed sea snails which 

 remain afloat by paddling a wide, fin-shaped foot. The latter group includes 

 the rare and highly prized Carinaria, the Atlanta shells and the shell-less 

 Firoloida. 



Not all pelagic mollusks live solely at the surface. The transparent, 

 delicate-shelled sea butterflies or pteropods (pronounced tero-pods) remain 

 several fathoms below the surface during the daylight hours but move up- 

 ward toward the surface at night. In many equatorial areas pteropods exist 

 in great numbers, and the steady rain of the sinking shells of the dead mol- 

 lusks litter the ocean's bottom many feet deep. Among the sea slugs, one 

 species of nudibranch (Scyllaea) is always pelagic, while the small and beau- 

 tiful Bat Sea Slug, Gastropteron rubrum, makes nocturnal trips from the 

 bottom of the shallow bay to the surface. The two pancake-shaped lobes of 



