Commemorating Dr Miguel Arrojado, Lisboa, Superintendent of a Brazilian railway company.

Small shrubs with cylindrical, sometimes segmented, stems and few branches. Ribs 7-40. Areoles of 2 kinds: those with flowers are condensed into ringed heads (cephalia), while those without flowers are separated, bristly and hairy. Flowers nocturnal or diurnal, small, often prolific, in either terminal or lateral dense areolar heads (cephalia), tubular, red, pink, violet or yellow. Pericarpel and flower tube naked. Fruit small, fleshy.

Fertile zones forming narrowed bristled constrictions around the stems; flowers often prolific.

About 10 species from E Brazil.