15. Diplodon websteri, Simpson.

It is the opinion of the Rev. Mr. Webster^* that I was not correct when I stated that I considered the above species as a D. menziesi in which the nodulous sculpture is developed to the highest degree. But we do find very interesting stages of nodulous development. My assertion is based on facts, and not on imagination. Webster seems to overlook the fact that we have a form of Diplodon which stands very near D. websteri —this is D. aucklandicus, Gray, which is considered by Simpson as a synonym of D. menziesi, and I have already stated that I accept his treatment of the two species.^† In fact, the aucklandicus form of D. menziesi and D. websteri are found living together! I have specimens of the former with the nodules so much developed that they approach Simpson's species very closely. The hinge, thickness of the valves, and brilliancy of the nacre are very variable in the genus, greatly influenced by the surroundings—the condition of the bottom, the quality, quantity, and mode of movement of the water. I consider D. websteri as a good subspecies of D. menziesi.