1879.] ^®& [Cooper. 



I have before shown that our west-coast banded group has claim at least 

 to be considered first cousin to the type of Helix, and cannot yet see more 

 than sub-generic differences, supposing lapicida to be the type. Mr. Bin- 

 ney, however, while admitting that the shell furnishes the most reliable 

 characters for the division (p. 252), makes it subordinate in most genera, 

 and appears to me to give it too little value. 



Sub-genus Arionta. 



I am more convinced by further comparisons of additional specimens that 

 the group of forms of this sub-genus found around San Francisco Bay are 

 merely local races of one species, the californiemis of Lea, running into 

 the var. nemorivaga Val. (usually called nickliniana Lea, which however 

 was so described as to include several), bridged Newc, passing into next, 

 ramentosa Gld. (nearly =- reticulata Pf. ), and the extreme Monterey race 

 vincta Val. (= californiemis of Binney). 



A specimen from Cedar Mountain, east of San Francisco Bay, found by 

 Dr. Yates, has nearly the form of var. vincta, being almost as high as wide, 

 but much dwarfed. Occasional specimens occur within the range of each 

 variety connecting it with some of the others. I suspect that the examina- 

 tion of numerous specimens of each would make the differences in internal 

 characters pointed out by Mr. Binney less uniform than he makes them ap- 

 pear, as he admits much variation in these respects in several species thus 

 examined. 



The named varieties of the European A. arbustorum are even more dis- 

 tinct than in our group inhabiting the region around San Francisco Bay. 



In the only admitted species of the Sierra Nevada, A. tudiculata, I have 

 before mentioned that many varieties exist, though less localized and 

 marked, only one having yet been named, the var. cypreophila Newc, 

 MSS. ; distinguished by thinness and umbilicus. This form, of very small 

 size, was also found by Dr. Yates in 1875, at Shasta, Cal., near lat. 41°, 

 the most northern point at which it has recently occurred. Nor does it pass 

 east of the Sierra Nevada, though lately included in the shells of the Great 

 Basin by Ingersoll, from misunderstanding the locality of "Bear River, 

 Cal.," given by Carlton. 



It may yet be proved that A. arrosa is but a sub-species of californiemis, 

 the varieties arboretorum Val., and the later varieties holderi and stiversi- 

 ana described by me, forming the connecting links. In that case A. exar- 

 ala Pf. must also fall into the series, being connected with arrosa by inter- 

 mediate specimens, though rare and local. But the very rarity of all these 

 links tends to indicate an original difference in the chief forms, now 

 becoming obscured where they meet in their ranges of distribution. (See 

 Amer. Jour, of Conch.. IV, 238.) 



In a recent article I have shown by maps the peculiar distribution of the 

 species I refer to, Arionta being grouped in narrow limits as compared with 

 the others. (Proc. Cal. Acad. Sc, V, 121, 1873.) 



Having now disposed of the Ariontas of the San Francisco group, there 

 remain those of Southern California, and the islands, extending onto the 

 peninsula. I have before shown in various articles that these are all con- 



