68 CLASSIFICATION. 



violence to most of the apparent affinities, whilst at the same time 

 it fails of signification even in one of the most important func- 

 tions with which it is connected, in that it does not enable us to 

 certainly separate the phytophagous from the zoophagous 

 animals, may be seriously questioned. We have many most im- 

 portant characters of the mollusks which impress themselves 

 upon their shells, so that they are in accord and enable us to 

 predicate reciprocall}^ their relationships ; and such characters 

 appear to me to be much more useful for classification. 



If it be proposed that a single arbitrary standard shall be used 

 because it is arbitrary and hence will remove all doubt as to the 

 position of a given species, then the standard selected should be 

 the most universal and the most ' apparent — namely, the shell. 

 But if a natural arrangement be attempted, still less can we 

 make account of any character which is not in accord with 

 the assemblage of characters. A natural sequence can only 

 result from an accordance of most of the organs and functions. 

 That dentition in the mollusks is a character worthy of study, 

 that it will throw light on many doubtful points, that it will cor- 

 rect many errors is not to be disputed ; but the claims made for 

 it are preposterous ; — for whilst a few hundred species only have 

 had their tongues examined, described and figured, many 

 thousands have been arbitrarily placed and displaced in conse- 

 quence. Stimpson has examined the tongue of Ranella caudata and 

 finds it to be that of a Murex ; accordingly he separates from 

 Eanella a few other species because their sheila resemble the shell 

 of Ranella caudata and unites them also with Muricidse and this is 

 practically the course (and necessarily so) pursued by all these 

 dentition systematists. If conchological characters maj' be used 

 to support the fabric reared upon the knowledge (I had almost 

 written the want of knowledge) of a single structural character, 

 why may they not lie equally used against it. Is it not imperti- 

 nent to make use of a few hundred observations of an organ 

 which only pervades a portion of the mollusca, to establish a 

 classification which is frequently in violent contrast with natural 

 affinities ascertained b}^ long examination of all the species, 

 recent and fossil ? 



If the exo-skeleton or shell carries the impi-ess of its animal, its 

 right appreciation will nfford us the only possible classification. 



