The third group of persons interested in the nomenclature 

 of the mollusks includes what may broadly be termed ama- 

 teurs. Many of these are lacking in a scientific background 

 and take up the collection of shells as a hobby, being attract- 

 ed no doubt by the endless variety and great beauty of these 

 natural objects. Even prehistoric men and modern savage tribes 

 have utilized shells for personal adornment and also as a me- 

 dium of exchange. In ancient as well as in modern times the 

 aesthetic appeal has provided an important stimulus for the 

 widespread interest in these forms. The contributions of ama- 

 teurs to this branch of science have been numerous and im- 

 portant, not only through the enrichment of the great central 

 collections by their activities in the field, but also through the 

 development of many specialists who have contributed greatly 

 to this branch of science. To facilitate the exchange of speci- 

 mens between collectors accurate naming was essential, and 

 as a result the taxonomy of the group was greatly empha- 

 sized. Since rarity and unusual forms, especially those with 

 differing color patterns or with unusual size or sculpture, led 

 to the description of many species which have later been in- 

 validated; it seems probable that as the polytypic character 

 of these forms is established many additional trivial names 

 will be suppressed. 



A fourth group interested in the nomenclature of mollusks 

 is represented by the palaeontologists, since it must be borne 

 in mind that these forms are subject not only to spatial isola- 

 tion, but to temporal isolation as well. The transition from 

 the late Tertiary forms to those of the modern age is not 

 sharply defined . Owing to the unique character of fossil forms 

 the relationship between the ancient and modern types has 

 often been obscured, and only the collection and study of 

 ample series has enabled taxonomists to clarify the resulting 

 confusion, especially in the case of polytypic forms. 



Still another group interested in the study of poyltypic 

 organisms includes those who see in these forms an approach 

 to the baffling problem of speciation in the living world. 



