Annuals, 5-30+ cm. Stems 1-11, erect or ascending, branched mostly proximally, glabrous or sparsely arachnose to puberulent and glabrescent. Cauline leaves: proximal mostly lance-linear, sometimes pinnately lobed, not fleshy, ultimate margins dentate or entire, faces glabrous or sparsely arachnose to puberulent and glabrescent; distal reduced subentire. Calyculi of 8-12+ lance-deltate to lanceolate bractlets, hyaline margins 0.05-0.3 mm wide. Involucres narrowly campanulate, 6-10 × 3-6 mm. Phyllaries 18-21+ in ± 2 series, lance-linear to linear, ± equal, hyaline margins 0.05-0.2 mm wide, faces glabrous. Receptacles not bristly. Florets 32-73: corollas yellow, 4-9 mm; outer ligules exserted 2-4 mm. Cypselae ± cylindro-fusiform to prismatic, 1.4-1.7 mm, ribs extending to apices, 5 more prominent than others; pappi persistent, of ca. 18, irregular needlelike teeth plus 1 bristle. Pollen mostly 4-porate (mean diam. 30 µm). 2n = 28. Flowering Apr-May. Coastal plains, beaches, dunes; of conservation concern; 0-40 m; Calif.; Mexico (Baja California). Malacothrix similis has been collected on Santa Cruz Island (in 1888) and at Hueneme Beach (in 1925).