The Jepson Manual II uses this name Hesperocyparis, but its not used elsewhere, and Kew has assessed all Conifers in their World Checklists of Selected Plant Families and they don't consider Hesperocyparis macrocarpa a valid name. http://apps.kew.org/wcsp/prepareChecklist.do?checklist=selected_families%40%40220080820132109259
While a previous set of taxon swaps moved trees from Cupressus to Hesperocyparis, this change moves them back for consistency with a broader number of taxonomies