These little beauties are Astrodapsis spatiosus, from the Late Miocene period.   They were collected from the Santa Margarita Formation in Scotts Valley, Santa Cruz County, California.   The largest one (on the right) is 38 mm (1-1/2") x 33 mm ( 1-5/16") and the smallest is 1-3/16" x 1-1/8".   The largest one is depressed orally, and I can't tell about the other two.   They are fragile, so further prep, although easy, is perilous.   As you can see, the apical systems are intact, and the periprocts of all of them are visible.  Lovely little things.