SI 



NOTES ON THE MORPHS ILLUSTRATED 

 IN THE ACCOMPANYING PLATES 



Morph I. Plate xvi. 



Long Island lies in the southern section of Willapa Bay in 

 southwestern Washington. The primitive type of sculpture, 

 exhibiting well defined secondary spiral bands and incipient 

 vertical lamellae, is very suggestive of a primitive condition, 

 pointing back to the ancestral stock. 



Specimens available for study, over 200. 



Morph 2. Plate xvii. 



In the receding shoreline on the eastern side of Willapa 

 Bay there is exposed an elevated bed of shells of Pleistocene 

 origin which contains an abundance of the shells of Thais 

 lamellosa. Samples of these shells are in the hands of the U. S. 

 Geological Survey for Carbon 14 dating, but at the time of 

 writing no report was available. As will be noted, the charac- 

 ter of the Thais population of the bay has not materially 

 changed during what must have been a considerable lapse of 

 time. 



Wood from the glacial till upon which the above shell bed 

 lies is reported to be over 35,000 years old as determined by 

 the Carbon-14 technique. Plate xiv. 



Specimens available over 100. 



Morph 3. Plate XVIII. 



The Thais populations of Willapa Bay, which is a body of 

 water about thirty miles in length, show some tendency to 

 develop local races, as may be seen on comparing Morph 3, 

 which is derived from Oysterville in the northern section of the 

 bay, with Morph i located a number of miles to the south- 

 ward. Since this bay is the center of an active oyster industry, 

 material containing Thais is apt to be shifted from one part 

 of the area to another. 



Specimens available, over 100. 



