370 CALIFORNIA ACADEMY OF SCIENCES. 



is calcareous. It has not been found west of this locality, 

 but reappears southward at Salinas River, and there borders 

 on the range of its nearest allies, Nos. 38 and 39, which, as 

 before stated, may be off-shoots from it in the cool coast 

 ranges. That it does not run into the Arionta group west- 

 ward, is shown by the forms of that sub-genus found with 

 it, being the two most unlike it known to exist. 



The most unexpected fact was finding No. 3i exactly like 

 the Monterey variety, which is elsewhere known only near 

 the coast, and rare. 



Livermore Yalley, which is about 80 square miles in area, 

 is too dry in summer for any species to live, except in very 

 rare spots along the banks of creeks where they may sur- 

 vive under logs, roots or stones, but we found none except 

 on the borders of a marshy lagoon, and the streams entering 

 it from the north or west, near where Alameda Creek cuts 

 through the western spur of the mountains. Those found 

 were Nos. 1, 1, 14, 31, 32, 33, 42, 43, 45 (Nos. 14 and 31 at 

 the base of the hills only). It is probable that the alkalin- 

 ity of much of the water in summer prevents the existence 

 of both land and fresh-water pulmonates in other parts of 

 the valley. 



It is well known that while springs containing little min- 

 eral matter except lime, are favorable to them, those having 

 much of other salts are injurious, which explains their ab- 

 sence from many regions where metamorphic or volcanic 

 rocks prevail, as well as from unaltered regions where salts- 

 have remained from marine deposits, or percolated through 

 from other rocks. 



The northern border of Contra Costa County would ap- 

 pear more favorable to tliem than we have found it to be, 

 but the summer wind blows through the gap with such force 

 as to desiccate the shores too much for the growth of many 

 trees, and west of the river junctiou the marshes are too 

 salt to suit them, so that there is very little shelter in the 

 dry season. Those known from there are Nos. 5, 11, 24, 25, 



