OF CONCHOLOGY. 223 



Monterey to about lat. 38°30 / , 150 miles, and inland to the east 

 shore of S. F. Bay. It may include, also, the northern Califor- 

 niensis. His H. Bridgesii, with the sculpture of the last and 

 the form of Nickliniana, as figured by Lea, is also found on the 

 east side of the bay only, and seems to connect the two, though 

 possibly a hybrid form. 



S. exarata, Pf., is a well-marked species, apparently not 

 mixing with the two preceding, which are its nearest allies. It 

 has quite a limited range, from Santa Cruz north to near S. F., 

 where it is very rare, and perhaps to Marin Co., not over 80 

 miles. 



H. seqiwicola, Coop., is as yet known only from a range of 20 

 miles north of Santa Cruz. It may be decided to be merely a 

 hirsute form of Dupetithouarsi, though otherwise different. 



Aplodon Columbiana, Lea, is first found here also. The ty- 

 pical form, with open umbilicus and no tooth, extends to Sitka 

 (Harford), where it is very fine. Dr. Newcomb gives as a form 

 "smooth, polished," but I believe they all are hirsute when 

 young, and scarcely ever lose the marks of hairs entirely. Thus 

 his twelve forms may be reduced to three [major and minor, 

 being merely extremes of size), and I consider one of the three 

 as : — 



A. germana, Gould, which was described from a dwarfed spe- 

 cimen, subangled, as the young always are. It is normally 

 dentate, umbilicus nearly or quite closed, and lip much nar- 

 rower than in Columbiana, also slightly flexuous. This form is- 

 not rare at Santa Cruz. Dr. Newcomb's third remaining variety 

 includes what I consider as hybrids of the two others, with the 

 characters more or less combined, as e. g., dentate and umbil. 

 open, toothless and umbilicus closed, or otherwise nearly inter- 

 mediate. 



San Francisco Bay. I include as one locality a district ex- 

 tending around this bay about 75 miles north and south, by 50 

 inland, nearly half as large as Massachusetts ; because most of 

 the species found here occur at many points if not all within 

 that range, and to enumerate each separately would take too 

 long. More species have been found within these limits than in 

 any district of the same size west of the Rocky Mountains, not 

 so much because it has been better searched, as because it is pe- 

 culiarly favorable to them. The cool sea-breeze constantly blow- 

 ing into the "Golden Gate" prevents so complete a drying up 

 of the land as takes place elsewhere to the south, and preserves 

 a uniformity of climate not found northward. This promotes a 

 growth of trees generally small and in scattered groves, but 

 essential to many Helicidce. 



