59 



The shells in this population are similar to those seen in 

 related forms, but the sculpture is somewhat coarser and the 

 size is much greater, both conditions presumably related to the 

 favorable environment afforded by the reef. The color pattern 

 is of the common intergrading type. 

 Specimens available, 25. 



Morph 24. Plate xxxix. 



Deadman's Bay is a shallow indentation in the western shore- 

 line of San Juan Island a few miles north of False Bay. Here 

 we encounter the transition from the lightly sculptured types 

 common in the region about Friday Harbor, and the rather 

 heavily imbricated forms which prevail to the northward. In 

 this population the intergrading from the relatively smooth 

 to the imbricated type presents a sculptural cline, with the less 

 imbricated individuals much in the minority. 



Coloration in this morph is absent or very feebly expressed. 

 The spire is moderately elongated. 

 Specimens available, 150. 



Morph 25 Plate xl. 



Mitchell's Bay is located on the northern section of the 

 western shoreline of San Juan Island. The specimens illustra- 

 ted were collected at a point about one mile south of the bay. 

 This population is obviously closely related to Morph xxxix, 

 which is located a few miles to the southward, but the shells 

 are more fully imbricated, and we find a few intruding banded 

 forms. It will be noted this type of imbrication is developed 

 through the almost equal elevation of both spiral and vertical 

 striae. 

 Specimens available, 100. 



Morph 26. Plate xli. 



North Pender Island is located to the northwest of the San 

 Juan group, in Canadian waters. The population illustrated 

 was collected from a reef in Shingle Bay. 



