THE 



QUAETERLY JOURNAL 



OF 



CONCHOLOGY. 



ON THE DIFFICULTIES OF EECOGNISINa '' NAMED 

 VAEIETIES^' ACCORDING TO THE ACCEPTED 

 AUTHORITIES. 



By T. KOGERS. 



A knowledge of the species of Land and Freshwater Shells 

 which are naturalised or indigenous to the British Isles is readily 

 acquired by the student of Conchology, and they are readily arranged 

 in the cabinets of collectors under their proper names and typical 

 characters, a few species excepted. 



The most difficult and most unsatisfactory part of the subject, 

 however, is that which relates to a proper knowledge of what are 

 known by Conchological authorities as " named varieties." This is 

 especially the case with such varieties as depend upon form or shape 

 for their chief varietal distinction. 



In studying the shells alone, as distinct from any variation which 

 may exist in the animals, the aberrant forms may be divided into 

 three or four divisions. First, and perhaps the least important, are 

 those variations which arise from colour or want of colour. This 

 would include the white varieties. The next would be those varieties 

 in which the texture, structure, thickness, and maximum and 

 minimum size of the shells aie noticed. This section would contain 

 the crystalline, iridescent, incrassate, and major and minor varieties. 



The next division, and that which I venture to think the most 

 important, is the one in which we recognise difference in form or 

 shape, this being the chief character under which specific differences 

 are arranged under generic characters, notwithstanding a great many 

 anomalies, such as the elevated and depressed spires, swollen and 

 compressed whorls of the helices, &c., abnormal contortions of the 

 planorbes or ventricose shells of the bivalves. It is in this division of 

 variation in which Conchological students find the most difficulty, 

 owing chiefly to the fact of not having some standard of variation 

 which would be understood by such terms used, as sxih-maritima, sub- 

 globosa, gigaxii, conoidea, obloiu/a, sub-scalaiis, &c., &c. 



Most students, I think, find that the brief technical language given 

 in books is inadequate to convey to the mind that which is intended. 

 If it should be within the means of the Editors of the Conchological 



