Thelocactus conothelos ssp. argenteus (Glass & Foster) Glass, Ident. Guide Threatened Cacti of Mexico 1: TH/CON (1997).

Basionym: Thelocactus conothelos var. argenteus Glass & Foster, Cact. Succ. J. (US) 44: 48 (1972).
Type: About 7 miles west of Ascensión, 12 February 1971, Glass & Foster 3176 (ZSS 3559).
Synonyms: Torreycactus conothele var. argenteus (Glass & Foster) Doweld, Sukkulenty 1: 19 (1998). Torreycactus conothelos ssp. argenteus (Glass & Foster) Doweld, Sukkulenty 3: 37 (2000).

Stem single, globose to elongate, 8-18 cm tall, 13 cm wide. Ribs indistinct. Tubercles conical. Areoles with glands. Central spines 4-6, 30-50 mm long, silvery to greyish, straight, acicular. Radial spines 20-25, 13-30 mm long, silvery to greyish, straight, acicular. Flowers 50-55 mm wide, magenta. Seeds 1.9 x 1.5 mm, testa cells conical with a smooth surface.

Mexico, Nuevo León, Valley of La Ascención, occurring in matorral xerofilo and pine forest on limestone hills, at elevations of about 1700 to 2100 metres above sea level. Its range lies within the Meseta Central subregion of the Chihuahuan Desert ecoregion.

This species distinguishes from the type for its dense white to silvery spination and the shredding central spines. The magenta flowers appear at the end of winter, from February to March, when higher temperatures and sunny days are needed by the plants to bloom.