CONCHOLOGY. 



taceous bodies, ascertaining the first to 

 consist only of carbonate of lime mixed 

 with gelatinous matter, while in the other 

 the presence of phosphate of lime was 

 detected. The cmstaceous body analy- 

 sed by Mr. Hatchett was the echinus. 

 "- All testaceous animals are composed of 

 two parts ; one of which, the animal it- 

 self, is soft and molluscous; the other 

 is the shell, or habitation, which is hard, 

 of a stony or calcareous nature, and ei- 

 ther partially or entirely covers the ani- 

 mal. The animal is attached to the shell 

 by means of ligaments or muscles. 



It was long considered as a matter of 

 dispute among naturalists, whether the 

 arrangement of shells should be consti- 

 tuted from the animals or their habita- 

 tion. No one can deny, that, if we pro- 

 ceed on principles strictly scientific, we 

 must regard them as a department of 

 zoology, and should, on that account, 

 dispose them according to the nature and 

 structure of the animals. But the classi- 

 fication formed from the characters of the 

 shells is universally followed, and we 

 must confess, too, is for many reasons 

 preferable to any other. Neither is it, in 

 the hands of the skilful conchologist, at- 

 tended with so much indecision as might 

 be generally imagined. 



In the first place, among the vast vari- 

 ety of shells hitherto discovered, how 

 small, comparatively, is the number of 

 those whose animal inhabitant is descri- 

 bed or known. It is not of species only 

 that we speak, but of whole natural fa- 

 milies or genera, not a single species of 

 which has been yet discovered with the 

 animal appertaining; so little are we ac- 

 quainted with the molluscous orders, or 

 animals inhabiting the shells. Of the 

 shells we daily see in collections few are 

 fished up alive, the far greater number 

 are found on shores, dead, or empty. 

 Neither, if it were otherwise, are accu- 

 rate descriptions of animals whose purls 

 are not easily seen, or anatomical inves- 

 tigations, which are in many cases neces- 

 sary, within the capacity of every one. 

 Many of their parts, and their respective 

 functions, are not to be ascertained, ex- 

 cept by comparative analogy, and which 

 in itself presents an insurmountable diffi- 

 culty, or a field of critical inquiry so ex- 

 tensive and complicated, that few, even 

 with the ability to pursue it with success, 

 could be prevailed upon to devote that 

 attention to the subject which it requires. 



Hence it becomes impossible to ar- 

 range the far greater number of testace- 

 ons productions by the animals ; the at- 



tempt must ever prove unsuccessful. Our 

 arrangements would be partial, and 

 three-fourths of the shells known must be 

 either excluded from the system, or bs 

 placed at hazard ; and of course without 

 order, or connection with those whose 

 animals we are acquainted with. The lat- 

 ter are chiefly such as are confined to the 

 coasts of the European seas, and some of 

 the terrestrial and fresh .water kinds, 

 which, from their abundance and locality, 

 have obtruded themselves upon the in- 

 vestigations of the naturalist. Even our 

 knowledge of those is exceedingly im- 

 perfect. 



The best characters, upon which to 

 found all systems of natural history, must 

 be those most obvious and accessible. 

 All ranks of animals, as nearly as can be 

 with convenience, should be arranged by 

 apparent and external characters. While 

 we study shells, without regarding the 

 animal, we are aware they are but consi- 

 dered partially. The animals that inha- 

 bit them should guide us in our re- 

 searches ; they alone are the fabricators 

 of the shell, and the shell is only their 

 habitation, to which they give the form, 

 the bulk, hardness, colours, and all the 

 peculiarities of elegance we admire. If 

 we were to examine these new and al- 

 most unknown beings, we should disco- 

 ver a number of parts as remarkable for 

 their structure as their functions, and an 

 infinite variety of curious and interesting 

 particulars relative to their general habits 

 and manners of life. It is a subject 

 worthy of the serious contemplation and 

 attention of the naturalist, and should 

 never be neglected when an opportunity 

 offers. But a system of conchology, . 

 founded entirely on the structure of the 

 animals, must, probably, ever remain one 

 of the desiderata of natural science. 



In the superficial arrangement taken 

 from shells alone we are not exempt 

 from difficulty. Shells vary exceedingly 

 in form and colour in the different stages 

 of their growth, and in this case we 

 should sometimes derive material assis- 

 tance from our knowledge of the animal. 

 Young shells have been described as 

 specifically distinct from the parent or 

 older shells by man}' writers. It indeed 

 requires a greater degree of caution in 

 determining the species, nay, even gene- 

 ra, of shells, in the different periods of 

 growth, than may be imagined ; of this 

 we could adduce many very remarkable 

 instances ; a few it may be necessary to 

 mention, to guard the common observer 



