274 Mr. W. Clark on the Chitonidae. 



XXV. — On the Chitonidce. By William Clark, Esq. 

 To the Editors of the Annals of Natural History. 



Gentlemen, Norfolk Crescent, Bath, Feb. 1, 1853. 



Before I entei* on matters, I beg to state, that a more extended 

 experience of the Mollusca has compelled me to relieve myself, 

 in part, of the assistance of conchological attributes, as I have 

 found them singularly defective and fallacious in reference to the 

 existing constitutions of divisions, families and genera; in support 

 of this view, I refer to many proofs in the various papers of mine 

 that have appeared in the ' Annals.' I therefore, as regards the 

 past, and henceforth, shall only consider the shell coverings of 

 the Mollusca as good and useful aids, in strict subservience to 

 the malacology of the animal, and as specialties, consequential, 

 and emanating from the vital organs ; and that the meaning of 

 whatever appellation may be attached to a division, family or 

 genus, has with me no reference to the testaceology : for instance, 

 speaking of the Muricidce, or its synonym, the Canalifera, the 

 shell is not in question, except as a corroborating incident, but 

 the animalia canalifera, whose mantles form canals ; and in like 

 manner, in mentioning the Holostomata, the entire periphery of 

 the aperture is not primarily intended, but, that the mantle 

 lining it is entire. 



The use of the word 'shell,' instead of 'animal,' in the construc- 

 tion of the subordinate divisions of a class, has doubtless arisen 

 from the ignorance of naturalists of the inhabitants ; but as this 

 cause is in a great measure removed, it is time to abandon a 

 system founded on fallacious bases, and have recourse to natiu-e's 

 imperishable land- marks. 



In these observations, I do not mean to say that conchology 

 is without its use : to palaeontologists, collections of shells are 

 the only resources to denote that their fossils present similari- 

 ties to many existing forms; but how infinitely more valuable 

 is an account of an existing animal, to inform them of the real 

 character of the relics of former epochs ! Beyond the restricted 

 points, conchology is totally unworthy to be the succedaneum of 

 the attributes of nature, and the ti'ue worshipers of the great 

 book will rejoice at the decadence of a usurpation to its just 

 limits. 



The Chitons have long been a source of diflference of opinion 

 with naturalists, not only as to their position amongst the 

 Mollusca, but it has been insisted on, that they are apocryphal 

 members of that class. The greatest authorities are in collision : 

 M. De Blainvillc considers that the motive power and other 



