64 



This morph is of unusual interest, since it diverges rather 

 widely from the basic type in this species . The spire is elon- 

 gated and the axial bands are, in most of the specimens, widely 

 spaced and much elevated. The spiral bands are also reduced 

 in number and accentuate the striking imbrication of the shell. 

 In this population there are however, individual specimens 

 that indicate a transition to the more normal type. 



The coloration is almost without exception of the mono- 

 chrome type, with various shades of orange and yellow pre- 

 dominating. There appears to be little indication of banding 

 except in the case of a few seemingly intrusive types. 



The size of the shells varies greatly, the larger specimens 

 coming as usual from the deeper niches, where they grow more 

 rapidly, with a corresponding modification of both size and 

 sculpture as shown in Plate lv, while in less favorable situa- 

 tions individuals of smaller or even dwarfed size arc produced, 

 as shown in Plate lxiv. 

 Specimens available, 50. 



Morph 41. Plate lvi. 



Fossil Bay is an indentation in the southeastern border of 

 Sucia Island in the San Juan group. 



In this population we find a very heterogeneous condition, 

 both as regards size, sculpture and coloration. In some of the 

 shells the sculpture lacks the axial bands and has indications 

 of the secondary spirals, which would suggest a reversion to 

 ancestral stock, a condition found in a number of popula- 

 tions at widely separated points. 

 Specimens available 150. 



Morph 42. Plate Lvii. 



The material representing this morph was dredged from a 

 submergedreef off the west coast of Whidbey Island. 



This population illustrates several points in the interpre- 

 tation of the variation found in these snails. It will'be noted 

 that the only significant effect of the adjustment of the snails 

 to this type of environment is apparently an increase in size, 

 the genetically determined characters of sculpture and colora- 

 tion remaining unaffected . Specimens available 25. 



