Cyclosa sierrae is a small spider with no common name. It is an orb weaver.
Cyclosa is a spider genus in the family Araneidae. Spiders of the genus Cyclosa build relatively small orb webs with a web decoration. The web decoration in Cyclosa spiders is often linear and includes prey remains and other debris, which probably serve to camouflage the spider.
Info from https://en.wikipedia.org/wiki/Cyclosa
Photos at Orkontas by George Konstantinou & Athalassa 3/4/2016, by Michael Hadjiconstantis