Fasciculithus richardii. Fasciculiths are an extinct group of Palaeocene nannoliths, possibly ancestral to the discoasters.They are formed of a single cycle of elements, with radial calcite c-axes. The element boundaries are indicated here by the red lines.
N.B. The main source for this figure was Perch-Nielsen 1971 (Bull. Geol. Soc Denmark, 21, p. 51-66: plate 8 fig. 2)