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PROCEEDINGS OF TEE NATIONAL MUSEUM. 



VOL. 49. 



single locality often exhibit a singular uniformity of characters, even 

 in factors which would seem not Ukely to be subject to influences of 

 the environment, such as the number of the major spirals. These 

 uniformities are probably due to inheritance from common ancestors. 

 The only way to get a broad view of the range of characters is to 

 have not only many specimens but specimens from many locaUties. 

 Then the gradations can be recognized in a way not otherwise possible. 

 There are some of these forms wliich exhibit characteristics of a 

 uniformity which entitles them to be called varieties, irrespective of 

 the differences due to color-variation, and other mutations. 



THAIS LAMELLOSA Gmelin, typical form. 



Type locality (to which it is by no means confined) Nootka Sound, 

 Vancouver Island. 



Shell large, heavy, with a conic spire shorter than the aperture in 

 most specimens, prominently laminated with from 9 to 20 sharp- 

 edged elevated lamellae, crenulated and produced where they inter- 

 sect a major spiral; on the penultimate whorl there are two, on the 

 last whorl seven to nine major and an indeterminate number of minor 

 spirals, the former most prominent near the shoulder of the whorl, 

 diminishing in size and more adjacent progressively toward the canal; 

 aperture large, the outer lip flaring, the throat sometimes dentate, 

 the umbiUcal chink usually sealed by callus (63873). 



In the following measurements in milHmeters the nucleus is not 



included : 



Measurements. 



TYPICAL FORM. 



