Berryessa is a Cantareus apertus, also known as the green snail, green garden snail, green burrowing snail and grunting snail (the latter because of a sort of squeaking sound it makes when disturbed).
D. and I found this snail crawling in a driveway in San José's Berryessa neighborhood one rainy Saturday afternoon, and she has come home with us to live with Remington (brown garden snail) and Ozzie and Harriet (garlic snails) in the terrarium.
Berryessa's shell is 17mm (5/8") in diameter, and she appears to be still a juvenile. Berryessa is also a he, because all land snails are hermaphrodite. S/he, like my other snails, eats pretty much the same fruit and veg I do, plus some powdered limestone for a strong, healthy shell.
I have been able to observe Berryessa's heart beating through a translucent portion of her shell. Snails have a 2-chambered heart, but it beats the same as yours and mine.
Berryessa's world, in the just-misted terrarium.