314 Studies Among- Mollusks. [zoe 



r 



theory that some of our more philosophical writers upon conch- 

 ology have suggested that shells might be arranged geographically 

 to represent the peculiar climatic conditions of the areas which they 

 inhabit. But our Helix, true to its paradoxical instincts, persists in 

 covering its shell with an epidermis as dark almost as the cuticle 

 of a Congo negro, and in shells of the same size and age, so far as 

 I have observed, scarcely a shade of difference in coloring can be 

 detected. In its dark coloring, as well as by the form of the shell, 

 Helix Newberryana agrees fairly well with the larger forms of our 

 American Zonites found south of the Ohio River. (Compare it 

 with Z. capnodeSy Z,fidiginostis and Z. siibplanus). Those Zonites, 



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however, inhabit a densely wooded region, with a moist, hot and 

 variable summer, and a moderately cold and wet winter chmate. 



On the coast of California its nearest allies, by the color of their 

 shells Helix fidelis , and its varieties infitmata, sitbearinata and mor- 

 77ionuni^ occupy the region north of San Francisco Bay. This 

 region in the localities where these shells are found, is also dense- 

 ly wooded and has a cool, foggy and moist climate the greater part 

 part of the year, the opposite conditions in almost every respect to 

 those prevailing in the region over which our southern snail ranges. 

 It will be seen by this that the color of Helix Newberryana cannot 

 be taken as an index of the climatic conditions of the area which 

 it inhabits. 



When we consider the variable nature of all our other west coast 

 land shells in form, size, color and sculpturing, the persistency 

 with which Helix Newberryana adheres to one unchanging form, 

 and its constancy In color and sculpturing, it is remarkable and a 

 puzzle indeed. 



Zonites (Mesomphix) Elliott: Redfield. 



This small shell is found quite plentifully in the mountains of 



North Carolina and adjacent States. It is constant in color, but 

 very variable in size. The late G. W. Tryon placed it at one time 

 in the genus Macrocyclis, which at that time included the forms we 

 now know as Selenites. 



In this mollusk and its shell we have another example in which 

 two genera are represented, one by the structure of the animal that 

 agrees with the genus Zonites, in having a caudal mucus pore 

 and a smooth or ribless jaw, and the other by the form and char- 

 acter of the shell, which agrees in every particular with the shells of 



