MALACOLOGY, 



forming many turns or evolutions, and constantly 

 alike in number in the different species of molluscs, 

 is a question not easily to be answered with any de- 

 gree of conclusive satisfaction ; we might quote seve- 

 ral opinions of high authority, but as they are contra- 

 dictory, and resting upon the speculation of ingenious 

 theories rather than upon anatomical data, we con- 

 sider them foreign to our present purpose, which is to 

 point out well-established facts, and not to launch into 

 doubtful ones. The subject is, however, worthy of 

 the naturalist's serious consideration, and we shall be 

 happy to find this suggestion worked upon by those 

 whose leisure will permit them to pursue it ; and, in 

 that study, much interesting information may be 

 gleaned from Mr. Gray's publication on the subject, 

 which we will not mutilate by abridgment here. 

 The operculum of shells must not be confounded with 

 a calcareous covering put on under peculiar circum- 

 stances by molluscs, to guard their bodies by closing 

 the aperture of their shells, as it totally differs in 

 its formation of parts, substance, and position, with 

 resrard to the animal, it is distinguished by the name 

 epiphragm, and is very often seen during the winter 

 on some species of Helix. Ninthly, the combined 

 form of the shell, the proportionate length of the 

 spire, and the shape of the opening in univalves, 

 with its direction, and various shaped parts, as in the 

 Columbella mercatoria, here figured. In bivalves, 



Columbella, 



the proportions of the valves on either side, their 

 markings and sculpture, and even their colour, the 

 presence or absence of an epidermis, with any other 

 clearly defined distinction of its whole appearance. 



According, therefore, to this rapid detail of the 

 considerations necessary to guide the malacologist in 

 distinguishing the various molluscs, with a view to 

 their scientific classification, the importance their rela- 

 tive characters offer in the different portions of their 

 organisation, and the necessity of examining atten- 

 tively their shells, to a certain extent, in order to 

 assist by the evidences they furnish of the animal's 

 structure, Conchology, as it has heretofore been 

 termed, is not altogether useless, though it is not by 

 any means indispensable. As, however, an examina- 

 tion of the beautiful armature of the animal may in 

 many cases lead to a more scientific acquaintance 

 with the place it occupies in the scale of creation, 

 the formation of conchulogical collections should 

 receive every encouragement. 



The basis of an arrangement which now em- 

 braces both them and their wonder-working ar- 

 chitects, must be founded on the general form oi 

 the animal's body, the distinction of a more or 

 less well-defined head, or of none at all, and the 

 organs of respiration which modifies the shape o 

 the shell, observing, always, that the same configura- 

 tion of shell sometimes, though rarely, is representec 

 by very distinct genera ; this, for example, is exem- 

 plified in the Haliolis, whose form exists in the pulmo- 

 branchiata, in the cismobranchiata, and in the otidea 



s the same with the patelloid, turriculated, and other 

 brms. These are the principles that have guided 

 yuvier, Lamarck, and their disciples in the classifi- 

 ation of molluscs, and formed that system which is 

 low universally adopted by naturalists of the present 

 day, or at least such of them as have kept pace with 

 he extended knowledge of the age we live in, and 

 he surprising facility given by accurate, elegant, and 

 cheap publications in every branch of it. Before we 

 iroceed to give some outline of this system of mala- 

 cology, we will shortly state some of those principles 

 jy which the distinction of species may be facili- 

 ated a part of the science by far the most difficult 

 n all the types of animal creation, but particularly 

 that under present consideration, arising greatly from 

 he circumstance of the shell having been made the 

 only guide for their distinctive separations or divi- 

 sions, and the determination of making them con- 

 tribute to the cause, without overturning altogether 

 the Linnsean school, in so far as its principles could 

 onsistently be adopted, and made conformable to 

 the far different view now taken of this subject. 



In the construction of a system, the great master, 

 Cuvier, has distinctly laid down some general rules, 

 to which it will be well always to attend, though 

 they are not always applicable ; in objects like 

 the present, our knowledge does not extend far 

 enough to pronounce without doubt on the singular 

 structure and less known habits of molluscs, we must 

 therefore approximate the species carefully and con- 

 sistently, according to the most obvious external 

 organisation in relation to the habits of the animal ; 

 should these agree, one principal step is gained in 

 forming a genus ; and the smaller differences form 

 an after-consideration, and establish the basis of con- 

 sistent sub-divisions. 



Cuvier says, " That the formation of systems is the 

 object of natural history, properly so called. Anatomy 

 receives them as it were ready made. The latter 

 takes its first direction from the former ; but it is not 

 slow in reflecting back the light it has received. By 

 applying a system of natural history to comparative 

 anatomy, we are speedily enabled to discover whe- 

 ther it deviates from the path of nature. The object 

 of every good method is to reduce a science to its 

 simplest terms, by reducing the propositions to the 

 greatest degree of generality of which they are sus- 

 ceptible. A good method must, therefore, be such as 

 will enable us to assign to each of its subdivisions some 

 qualities common to the greater portion of the organs. 

 This object is to be attained by two different means, 

 which may serve to prove or verify each other ; and 

 that to which all men will naturally have recourse, is 

 to proceed from the observation of species, to unite 

 them in genera, and to collecting these in a superior 

 order, according as they find themselves conducted 

 to that classification by an examination of the whole 

 of their attributes. The second, and that which the 

 greater part of modern naturalists have employed is, 

 in the first instance, to fix upon certain basis of 

 division, agreeably to which, beings, when observed, 

 are arranged in their proper places. The first mode 

 cannot mislead us ; but it is only applicable to those 

 beings of which we possess a perfect knowledge ; the 

 second is more generally practised, but it is subject to 

 error. When the bases that have been adapted remain 

 consistent with the combinations which observation 

 discovers, and when the same foundations arc again 

 pointed out by the results deduced from observation, the 



