MOLLUSCS. 325 



The Iaxtiiixidj: are remarkable for the beautiful ]>urj)le color of their thin shells. 

 Tliey are pelagic, oceanic snails, which lead a predaceous life. At times on the high seas 

 the navigator encounters vast numbers of them, forming immense schooKs, and feeding 

 upon the other forms of life ; medusiB, Crustacea, etc., with which they are surrounded. 

 The animal has a large head furnished with an extensible proboscis. The eyes ai"e 

 minute and situated on the extremities of the ocular peduncles, while the foot is small 

 and divided. The shells are thin and delicate, the whorls of the spiral being few in 

 number. At the base they are of a deep violet color, but the apex is nearly or entirely 

 wliite. 



One of the most interesting features connected with these shells is the enormous 

 float wliich they form to support the eggs. The foot seo'etes a glutinous secretion 

 which hardens to a slight extent when brought in contact with the water. During the 

 reproductive season the formation of this egg float is continuous, and, as it is formed, 

 e<;gs are fastened to its lower surface. From this mode of formation, that part of the 

 float farthest from the animal contains the most advanced eggs ; and, in fact, the eggs 

 in this portion may have hatched and the embryos have begun their free life ere those 



thina, purple shell, with the float supportiug the eggs. 



nearest the l)ody have passed through the earlier stages of develo|)ment. Although 

 the parent usually carries the float attached to the body, still it has ajiparently the 

 power to cast it off at will, while the action of storms usually separates the mother 

 from the egg. When thus cast adrift, the float still sustains the eggs, and they ])ursue 

 their development as usual. Each egg is fastened to the float by a short peduncle, 

 while the float itself is composed of numerous little bubbles, thus securing great 

 buoyant ]iowers. 



The lanthinm do not ap])ear to have the jiowerof sinking in the water unless the 

 float is detached, and so at the time of storms they are frequently cast upon the shores 

 in large numbers. At such times they are utterly helpless and make no attempts to 

 crawl. They, however, frequently adhere to each other by means of the foot, and, 

 when handled, secrete a violet-colored fluid. 



lanthina, the most prominent genus, contains about ten species, one of which {I. 

 frcu/ilis) is occasionally thrown up on the southern New England coasts by severe 

 southeast storms. It is not jirojierly a member of the American fauna, but like the 

 rest of the genus is an inhabitant of the high seas. The only other living genus of 

 the family (liecliisin) is covered with a brownish epidermis. Like Tant/iino, it forms 

 a float. 



The S0LAEI.D.E cml)races a group of molluscs which, from the shape of the shell, 

 was formerly included in the Trochidae. The shell is orbicular and forms a more or 



