6o 



In this morph it will be noted the sculpture is very similar 

 to that seen in morphs 24 and 25, and the same type of gra- 

 dational condition is in evidence, but the main spirals are more 

 developed and the percentage of colored individuals is greatly 

 increased. 

 Specimens available, roo. 



Morph 27. Plate xlii. 



Morse or Ship Island is a small rocky islet located at the 

 northern end of San Juan Island. 



The sculpture in this population is similar to that found in 

 morphs 24, 25 and 26, but the imbrication is as a rule more 

 heavily developed, and leads by a graded series to forms resem- 

 bling the extreme types illustrated in morphs 34 and 35, the 

 group forming a clinal sequence. Coloration is lacking or is 

 feebly expressed. 

 Specimens available, 100. 



Morph 28. Plate xLiii. 



St. John's Harbor is located in the Bardwell group of islands 

 in Milbank Sound, Alaska. 



The striking similarity of this Alaskan morph to populations 

 inhabiting the San Juan Islands, is one of the many illustra- 

 tions of the appearance in this protean species, of seemingly 

 almost identical phenotypes at widely separated points. The 

 tendency towards the development of an elongated spire is 

 characteristic of many of the northern forms. 

 Specimens available, 25. 



Morph 29. Plate xliv. 



Blakeley Island is one of the larger members of the San 

 Juan group. The specimens illustrated were collected at a 

 point on the northern shore, northeastward of Peavine Pass. 



This morph is marked by an unusual development of pig- 

 mentation, with a preponderance of banded forms. A few pale 

 specimens present are not shown in the plate. The sculpture 

 suggests a slight cline in the degree of imbrication. 

 Specimens available, 25. 



