Bull. Torrey Bot. Club 32: 540. 1905.
Subshrubs. Stems erect, 80–330 mm, glabrous. Leaves cauline, relatively even-sized; petiole absent or short; blade narrowly ovate to elliptic-lanceolate, elliptic, or oblanceolate, 20–50 × 3–15 mm, margins dentate to serrate, plane or revolute, apex obtuse to acute, surfaces glabrous. Pedicels 3–10 mm in fruit. Flowers 2 per node, chasmogamous. Calyces inflated in fruit, 35–40 mm, glabrous, tube distinctly dilated distally, lobes subequal, apex acute, ribs green, intercostal areas light green. Corollas pale-yellow to cream or nearly white, pale orange, golden yellow, or orange-yellow, not spotted or striped, palate ridges golden yellow, throat internally glabrous, tube-throat 37–52 mm, limb 15–22 mm diam., not bilabiate, lobes entire. Anthers exserted (at throat), glabrous. Styles minutely glandular. Stigmas exserted, lobes equal. Capsules 20–36 mm. 2n = 20.
Phenology: Flowering Apr–Jun.
Habitat: Rock walls, dry rocky soils.
Elevation: 200–1500 m.
Diplacus aridus is known from Imperial and San Diego counties.