364 CALIFORNIA ACADEMY OF SCIENCES. 



Salinas valley, which no doubt contains them through- 

 out, as .Or. Yates found them living at the river 

 crossing, 90 miles northward, near Monterey Bay. There is 

 a gap of 70 miles from there to Cedar Mountain where the 

 species has not been found, nor indeed any other more than 

 25 miles east of the coast, but this must be on account of 

 no search having been made thoroughly enough. It seems 

 ^Iso quite probable that links between H. traskl and H. mor- 

 7)iomim will be found in the Sierra Nevada. 



3. THE BAY REGION, LAT. 36"^ 30' TO 38° 30'. 



I now come to the most productive region in California as 

 to Land Pulmonata, about 45 out of 80 forms knoAvn in the 

 State being found in it, having beeo the most thoroughly 

 searched and naturally having the most suitable conditions 

 for this superiority in numbers. I give a map, copied from 

 the State map of Prof. Whitney's Geological Survey, with 

 the exception that ths elevations are indicated by contour 

 lines of 500 feet each, anil the heights of tho measured peaks 

 ^'iven in feet, with somj corrections furnished by Prof. Da- 

 vidson of the Coast Survey. Being triangular in form and 

 approximately 150 by 96 miles in extent, it comprises about 

 7,200 square miles of land. Of this I have myself traversed 

 -carefully more than half on foot or horseback, especially 

 the mountainous parts, when wbrking out the geology of the 

 ■" Bay Map," which includes four-sevenths of the land here 

 given. The northeast marshy and Hat corner of the region, 

 about 870 square miles in extent, is not known to produce 

 any but the amphibious Succineas, except a few washed 

 down by mountain streams, which survive along the borders 

 of the marshes for a short tima, and might increase if not 

 trampled on by cattle in the dry season. 



This region lies directly west of the most elevated por- 

 tion of the Sierra Nevada, which also produces the greater 

 part of the Pulmonata characterizing that range, as men- 

 tioned previously. The same influences affect both regions 



