Plate P5. Scale bar = 10 µm. 1A, 1B. Sphenolithus radians (Sample 183-1135A-22R-CC; crossed polarizers). 1C, 1D. Sphenolithus radians (Sample 183-1135A-20R-4, 100-101 cm; crossed polarizers). 2A, 2B. Sphenolithus moriformis (Sample 183-1135A-20R-4, 100-101 cm; crossed polarizers). 3A, 3B. Tribrachiatus orthostylus (Section 183-1135A-22R-CC; transmitted light). 4. Sphenolithus primus (Sample 183-1135A-25R-1, 25-26 cm; scanning electron microscope).

Plate P5. Scale bar = 10 µm. 1A, 1B. Sphenolithus radians (Sample 183-1135A-22R-CC; crossed polarizers). 1C, 1D. Sphenolithus radians (Sample 183-1135A-20R-4, 100-101 cm; crossed polarizers). 2A, 2B. Sphenolithus moriformis (Sample 183-1135A-20R-4, 100-101 cm; crossed polarizers). 3A, 3B. Tribrachiatus orthostylus (Section 183-1135A-22R-CC; transmitted light). 4. Sphenolithus primus (Sample 183-1135A-25R-1, 25-26 cm; scanning electron microscope).