57 



Morph 17. Plate zxxii. 



Smith Island is an extremely isolated reefy islet, situated at 

 the eastern end of the Strait of Juan de Fuca. The shore is 

 covered with large glacial boulders, which constitute a rather 

 unfavorable environment, and as a result the shells are reduc- 

 ed in size. This morph belongs in the large group of populations 

 in which the sculpture is reduced and the coloration is lacking 

 or feebly expressed. 

 Specimens available, 150. 



Morph 18. Plate xxxiii. 



The village of Friday Harbor is located on the bay bearing 

 the same name, on the eastern side of San Juan Island. A dock 

 has been in existence at this point for many years, and it is 

 presumed the population of snails present on the dock piling 

 originated from a group already present on the adjacent shore 

 or by migrants from near-by Brown Island and Point Caution. 

 The shells are for the most part very similar in form and sculp- 

 ture to those found on adjacent areas, while their large size 

 suggests the superior nutritive conditions commonly found in 

 such situations. 

 Specimens available, 100. 



Morph 19. Plate xxxiv. 



North Beach is within the city-limits of Seattle. The popu- 

 lation found here is of a type having a very wide dispersal 

 throughout Puget Sound and adjacent areas, while forms of a 

 very similar appearance occur in California and Alaska, indi- 

 cating along with other phenomena, the common genetic back- 

 ground of the entire lamellosa complex. In this group of morphs 

 the spire is relatively short and the sculpture is feebly devel- 

 oped or obsolete. In the great majority the typical graded 

 type of color is in evidence. Illustrations given for this morph 

 compare closely with some of those figured for morph 5 from 

 Alameda in San Francisco Bay. 



