NOTES ON THE SHELLS OF THE GENUS EPITONIUM AND 

 ITS ALLIES OF THE PACIFIC COAST OF AMERICA. 



By William Healet Dall, 



Honorary Curator of Mollusks, United States National Museum. 



The genus called by Lamarck, in 1799, Cyclostoma (type, Turho 

 scalaris Linnaeus) is more commonly known by the name of Scalaria, 

 which he adopted in 1801. As this shifting of a name once given is 

 inadmissible under the rules of nomenclature we are obliged to look 

 further for the proper name of the genus. 



In the anonymous Museum Calonnianum printed "by the dealer, 

 George Humphrey, after a manuscript of Hwass in 1797, the name 

 Scala is used, and for some years the present writer adopted it for 

 the genus. However, the inconveniences incident to the adoption of 

 the nomenclature of this publication are so great that the Interna- 

 tional Committee on Zoological Nomenclature have decided to ex- 

 punge it from the list of works to be cited in nomenclature, and 

 the next name in order, Epitonium of Bolten in 1798, must be 

 adopted. 



The group is distributed all over the world and is usually rich in 

 species, but sparse in individuals in any given fauna. E. de Boury 

 has given much attention to it, and it is to be hoped his proposed 

 monograph may not long be delayed since such excellent illustra- 

 tions of the species as those he has published on minor groups are 

 urgently needed to identify the many closely related forms. Many 

 of the older descriptions are so brief as not to permit of the differen- 

 tiation of similar species, and even the figures, especiaUy of the 

 smaller species, are more or less inadequate. 



Among the principal features serving to identify the species are the 

 presence or absence of spiral sculpture, of an umbilical perforation, and 

 of a basal cord or disk. The number of the varices is, on the whole, very 

 constant in most of the groups, following the rule that the greatest 

 variation will be found where the normal number of varices is great- 

 est. In a species with few varices the number is remarkably con- 

 stant, except in the group typified by E. lineatum Say, where the 

 number is irregular and the varices coarse and very few. The nu- 

 cleus or nepionic shell is pretty uniform throughout the group, usu- 



Proceedinqs U. S. National Museum, Vol. 53-No. 2217 



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