354 Mr. W. Clark on the Littorinidae. 



inclined to reduce the true specific types to L. neritoides, L. lit- 

 torea, L. littoralis and L. rudis." 



My views being thus supported, I send forth without hesita- 

 tion these observations made long ago, and I feel gratified that 

 my investigations of this tribe have received the corroboration 

 enunciated by that eminent Professor. 



Before I give the descriptions of the types of the genera of the 

 Littorinidce, I will make some remarks on the prevalent practice 

 of naturalists to create species from mere varieties : this anxiety 

 can only be attributed to their wish to extend our knowledge of 

 new and interesting objects : that these views are desirable and 

 laudable cannot be questioned, but it is to be feared that the zeal 

 of these gentlemen, combined with the ardour of rivalry in the 

 race with their brethren in the same pursuits, have been the 

 cause of a departure from those principles and laws which are 

 considered indispensable to arrive at just conclusions in the esta- 

 blishment of genera and species ; or in other words, in laying 

 down the true bases of the differential features of the families, 

 genera and species of a class, so as to enable the student to de- 

 posit his objects with certainty in their natural position, and to 

 distinguish them from others, however numerous, of the same 

 family, by concise and well-defined specialties. If these rules 

 were rigorously attended to, we should have fewer complaints of 

 the almost impossibility of identifying many of the objects of 

 natural history. The inconveniences that have arisen from the 

 neglect of these precepts are so great and pressing, that I pro- 

 pose to attempt to point out their origin, and suggest a remedy 

 as far as regards malacology and conchology, and to evidence 

 and illustrate my arguments by references to the present state of 

 certain groups of the Mollusca. 



If conchologists are determined to form numerous species from 

 mere varietal conchological indicia, they must have their way, but 

 malacologists will not concur with them to give a dozen names 

 to the same animal. These gentlemen cannot escape having the 

 phrase a Dies docebit " verified ; the day of retractation will as- 

 suredly arrive; it will therefore be better for the interests of 

 science and their amour propre, at once to apply the remedy for 

 this singular creative monomania, 



. . . . " O medici mediam pertundite venam." 



I apologise for my irreverent quotation, and trust I may claim 

 for this once, 



" Liberius si 



Dixero quid, si forte joeosius, hoc mihi juris 



Cum venia dabis." 



The practice I have just described is fraught with great detri- 



