SUMMARY OF THE SHELLS OF THE GENUS OONUS FROM 

 THE PACIFIC COAST OF AMERICA IN THE U. S. 

 NATIONAL MUSEUM. 



By William Healey Dall, 



Curator, Division of Mpllusks, U. S. National Museum. 



Thcresearches of Bergh have shown t hat t lie genus ( 'onus is a very 

 natural one, and that, while the anatomical characters show, like tho 

 shells, considerable variation, there is no evidence as yet of any 

 distinctly characterized groups, anatomically speaking, which would 

 enable ns to divide the genus in harmony with the conchological 

 characters or on the anatomy alone. The color pattern, the general 

 form, and sculpture of the shell still remain the most constant, as 

 they certainly are the most convenient, characters for separating the 

 genus into sections. 



A study of the coloration of the species leads one to believe the 

 range of variation among the species to be greater than conchologists 

 have usually been ready to admit. On the other hand, the identifi- 

 cations made from imperfect figures are responsible for much con- 

 fusion among similar but not identical things. 



Among cones of several groups, such as the Proteus group, the 

 Nebulosus group, and the Brunneus group, the coloration, on careful 

 study, is seen to consist of a mingling of several distinct elements, 

 each of which has its distinct series of variations. The combinations 

 resulting are therefore quite numerous and, without close study, give 

 very different aspects to the shells, thus obscuring their relations to 

 each other. 



In most cases there are nebulous masses of color which contrast 

 with the ground color of the shell and may be paler or darker, are 

 usually disposed in a nebulous manner without any well-defined 

 pattern, and sometimes are concentrated in axial streaks or flames. 



There is a tendency for these masses of color to become less con- 

 spicuous near the shoulder, at the middle of the whorl, and near the 

 base, giving rise to more or less distinct spiral bands or lighter areas 

 in these areas of the surface. The axial streaks before mentioned an* 

 apt to be broken or angulated where they cross these areas, thus 

 giving rise to distinct, spiral, usually lighter, color bands. 



Proceedings U. S. National Museum, Vol. 38— No. 1741 . 



LM7 



