476 MUEICID^E. 



grounds. Many causes have concurred to produce this arti- 

 ficial arrangement ; amongst them, the multitude of species, 

 the dissimilarity of the hard parts, which malacologists failed 

 to see in their true light as the indices of species, choosing to 

 consider the variable forms to proceed from generic animal 

 distinction. We will examine these points, and endeavour to 

 reduce them to their proper value. 



The principal distinctions between this division and the 

 Holostomata are, that the periphery of the aperture of the 

 shells of the Canalifera is broken into branchial canals and 

 more marked and extensive depuratory sinuses, and that the 

 soft parts have invariably present a retractile proboscis, with 

 some other variations that will be mentioned. The shells 

 are of elegant structure and the animals of great beauty, 

 but the latter resemble each other so much as only to admit, 

 agreeably to my method, of the constitution of the single genus 

 Murex, and even to render specific characters difficult without 

 the aid of the hard parts, on which account I am obliged to 

 enter upon more minute details than perhaps may be thought 

 necessary. It will also be shown that the anatomy, as well as 

 the hard and soft parts, with the general characters of the co- 

 loration, especially in the minor Murices, are all but identical. 



There is a singular coherence in the specific descriptions ; 

 this arises from the similarity of the objects ; but if, to relieve 

 the tedium of the " iterumque, iterumque," I had attempted 

 a generalization beyond what has been admitted, confusion 

 would have resulted from the destruction of the individuality 

 of the objects by amalgamated descriptive characters; the 

 account would rather be that of a compound than of an indi- 

 vidual animal, and the more delicate features so essential for 

 specific comparison lost. If animals are to be described cor- 

 rectly, conciseness must give way to particular description; 

 indeed, in zoological matters, the term serves for little else 

 than to express the omission often of very essential features : 

 but if it be insisted on, we must rest content with rough 

 sketches instead of finished portraitures. 



The general distribution of the Muricidte, according to my 

 method, includes Lamarck' s Purpurifera, which have, as I 



