204 Mr. Gray's Conchological Observations. 



From these observations we may then conclude that the whole 

 of the reasoning upon which the theory of their vegetable nature 

 is built, is derived from a gratuitous assumption, that certain 

 bodies which have been called sponges, and which probably pos- 

 sess a vegetable structure, are of the same nature as the true 

 marine species. In opposition to this we have the opinions of the 

 most accurate and observing naturalists, the concurrence of anal- 

 ogy, and the support of plain and intelligible fact : and the con- 

 clusion to which I think we must come, is, that they are of a 

 true animal structure ; — though it must be left to further investi- 

 gation to ascertain their relations to other animals, and their exact 

 situation in the scale of animated nature. 



Art. XXIV. Conchological Observations, being an attempt 

 to jix the study of Conchology on a firm basis. By 

 Mr. John Edward Gray, M.G.S. 



|. 1. On the Structure and General form of Shells. 



It has been a general source of complaint among Conchologists, 

 that many of the terms usually employed in this beautiful study 

 are extremely ambiguous ; owing to the ignorance that formerly 

 existed with respect to the animals which form them, as well as 

 to the mode of their formation ; while other terms, the results of 

 a depraved imagination, are so indelicate, as to render the use of 

 them on many occasions improper. In the present Essay which 

 I propose to devote to the consideration of the terms which should 

 be employed in Conchology, while I avoid the latter error, I shall 

 endeavour to obviate the forirer, by more accurately defining 

 their meaning. For this purpose it will be necessary to take the 

 inhabitants of shells into consideration, which will enable me to 

 give at the same time such rules as may point out their most essen- 

 tial difference, and thus lead to the perfect understanding of the 

 shell itself, e v en when the animals (which it should be the aim of 

 all Conchologists to procure) are unfortunately wanting. 



