The genus Thelocactus 

Thelocactus schwarzii Backeberg, Cact. Succ. J. Gr. Brit. 12: 81 (1950).

Thelocactus Schwarzii sp. n.
   Simplex, ad 6 cm. altus, glaucinus; ca 5.5 cm. latus; costis paene omnino tuberculatis (!), 13, tuberculis ad 13 mm. longis, 9 mm. latis; areolis oblongis, ca 2 mm. longis, albidis; aculeis centralibus 0 (!), radialibus 13—14, lateraliter radiantibus, vel flavidis vel primum basi rubicundis deinde omnino flavidis, 3 superioribus aliquid applanatis, 2 ad 17 mm. longis, supremo ad 27 mm. longo, incurvato; floribus ad 8.5 cm. latis, roseo-purpurascentibus, fauce coccinea; tubo viridi; squamis acutis; antheris flavidis, stylo albo, stigmatibus roseo-coccineis.

   Simple, more or less 6 cm. high and ca 5.5 cm. in diameter; a little bluish green; 13 ribs, nearly entirely tuberculate, tubercles to 13 mm. long and 9 mm. broad; areoles oblong, ca 2 mm. long, very short whitish felt; no central spines, radial spines 13—14, horizontally spreading, a little recurved to the body of the plant, yellowish, or at first with red base, later quite yellowish, the 3 upper spines more or less a little flattened, two of them to 17 mm. long, the uppermost to 27 mm. long, more flattened and curved at the apex; flowers to 8.5 cm. broad, reddish purplish with scarlet throat; green tube with acute scales; anthers yellowish, style white, stigma lobes reddish scarlet. Mexico, Tamaulipas, on plains, under bushes in heavy clay soil.
   The inner perianth segments show a white zone above the scarlet throat.
   This plant differs from Thelocactus bicolor and its variations in that it has no central spines, more ribs (13 instead of 8) and the ribs consisting of perfect tubercles. There is a dark green v. texensis of T. bicolor not described hitherto, which also has a flattened upper radial spine, but ribs are less tubercled, eight ribs only as in the type, and one central spine.    The above described plant is also less conic and represents a well characterised species, the radials more appressed as in other forms. The plant was found by F. Schwarz and sent under No. 9.