LECTURES ON MOLLUSCA. 153 



of the animal, (called the mantle,) the head and foot, and other im- 

 portant members, not leaving any impress on their unpliant covering. 



It is only of late years that enquirers have even attempted to gain 

 information about the animals of shells. The very beauty of the shell 

 has contributed to this result. Every sailor could collect shells, and 

 every lady could lay them on cotton in a drawer ; the animal was a 

 nuisance, liable to rot if not carefully extracted, only to be preserved 

 in buttles of spirit, and then presenting nothing but a shriveled or 

 shapeless mass, fit only for the dissector's knife. Even the figures of 

 living animals in the works of scientific voyagers are by no means in- 

 fallible, it being not uncommon to find voracious proboscids figured 

 with a vegetarian snout, or to see the shell turned the wrong way on 

 the back of the crawler. When it is remembered that a large pro- 

 portion of "shell-fish" live in deep water; that even those which 

 surround our coasts can be but seldom examined in their natural con- 

 dition ; that very few will breed in confinement, and that travelers are 

 very seldom able to dissect and examine microscopically, or even to 

 draw correctly while on their expeditions ; we must be content to wait 

 many years before this branch of natural history is as satisfactorily 

 established as other branches of popular science. 



Let not this, however, deter any one from its pursuit. If we only 

 collect, arrange, and study shells, we are doing something. We at 

 least prepare a store of materials for future use. And every one can 

 examine alive and report upon the shells of his own locality, whether 

 land, fresh water, or marine. There is not a schoolboy, or a western 

 farmer, but what may be not merely a learner of what others have 

 done, but a gainer and teacher of fresh knowledge : while to those who 

 can engage in scientific travel, there is open a field of original research, 

 such as but few branches of science have left untrodden. At the present 

 moment, we cannot agree upon the main divisions of our classification 

 of shell-fish, for want of knowledge of the animals, habits and food of 

 some of the commonest shells, which are annually collected by the hun- 

 dred or the thousand merely for the purposes of trade. 



In old days, when every one followed Linnaeus, it was easy to count 

 whether a shell had one, two, or many valves, and name it, with con- 

 fidence that its jDlace would not have to be disturbed. In the second 

 epoch of study, after Cuvier had introduced an approximation to a 

 natural system, all the world laid aside the artificial method, and 

 arranged their books and shells according to the system of Lamarck. 

 But now that we are as much in advance of Lamarck as he was of 

 Linnaeus ; and every fresh animal that is examined may alter our clas- 

 sification ; we must be content to alter and amend our books with every 

 succeeding edition, and not allow ourselves to consider anything as 

 fixed. The arrangement proposed in these pages may serve as an 

 approximation to the truth, or as a starting point to begin from ; 

 neither ignoring recent discoveries, nor departing from recognized 

 facts without better authority than hasty observations. 



Another difficulty is much more serious. Most of the early natu- 

 ralists, and many in our own day, have been in the habit of naming 

 shells without describing them ; or have described them so loosely that 

 it is a matter of opinion only what they meant by their words ; or have 



