Herbs, annual. Stems erect, 80–120 mm, glandular-pubescent. Leaves cauline, nearly even-sized or enlarging distally; petiole absent or with petiole-like extension; blade ovate to obovate, 12–41 × 5–21 mm, margins entire or crenate, plane, usually ciliate proximally, apex obtuse, surfaces glandular-pubescent. Pedicels 3–5 mm in fruit. Flowers 2 per node, or 1 or 2 per node on 1 plant, chasmogamous. Calyces distinctly asymmetrically attached to pedicel, not inflated in fruit, 18–21 mm, glandular-pubescent, lobes subequal, apex acute, ribs usually green, intercostal areas whitish. Corollas: throat magenta, abaxial lip magenta, adaxial lip whitish, palate ridges not seen, tube-throat 20–23 mm, limb 4–5 mm diam., bilabiate, lobes of abaxial lip smaller than adaxial. Anthers (distal pair) nearly exserted, glabrous. Styles puberulent distally. Stigmas exserted, lobes unequal, abaxial 6–8 times adaxial. Capsules not seen.
Phenology: Flowering Mar–Apr.
Habitat: Rocky, brushy slopes.
Elevation: 0–100 m.
Diplacus traskiae is known only from Santa Catalina Island. According to the California Native Plant Society Online Inventory of Rare and Endangered Plants, ed. 8 (http://www.cnps.org/cnps/rareplants/inventory/), it (as Mimulus traskiae) is possibly extirpated.