Plate P11. Rhomboaster, Tribrachiatus. Taxonomic organization and concepts are generally comparable to those of Young and Bown (1997) and Bown (2005). Images with black background are cross-polarized light images; those with light backgrounds are phase-contrast images. 1–12. Rhomboaster cuspis; (1–5, 7–9) Sample 198-1208A-36X-CC, 4 cm, (6, 10–12) Sample 198-1208A-36X-CC, 5 cm. 13–23, 25–27. Rhomboaster bramlettei (Sample 198-1208A-36X-CC, 4 cm); (22, 23) side view. 24. Rhomboaster bramlettei-spineus (Sample 198-1208A-36X-CC, 4 cm). 28, 33. Tribrachiatus orthostylus; (28) Sample 198-1208A-36X-CC, 1.5 cm, (33) Sample 198-1208A-36X-CC, 4 cm. 29–32, 34–36. Tribrachiatus contortus; (29–32) Sample 198-1208A-36X-CC, 5 cm, (34, 35) Sample 198-1208A-36X-CC, 4 cm, (36) Sample 198-1208A-36X-CC, 2 cm. 37–39. Tribrachiatus digitalis (Sample 198-1208A-36X-CC, 8 cm). (Plate shown on next page.)

Plate P11. Rhomboaster, Tribrachiatus. Taxonomic organization and concepts are generally comparable to those of Young and Bown (1997) and Bown (2005). Images with black background are cross-polarized light images; those with light backgrounds are phase-contrast images. 1–12. Rhomboaster cuspis; (1–5, 7–9) Sample 198-1208A-36X-CC, 4 cm, (6, 10–12) Sample 198-1208A-36X-CC, 5 cm. 13–23, 25–27. Rhomboaster bramlettei (Sample 198-1208A-36X-CC, 4 cm); (22, 23) side view. 24. Rhomboaster bramlettei-spineus (Sample 198-1208A-36X-CC, 4 cm). 28, 33. Tribrachiatus orthostylus; (28) Sample 198-1208A-36X-CC, 1.5 cm, (33) Sample 198-1208A-36X-CC, 4 cm. 29–32, 34–36. Tribrachiatus contortus; (29–32) Sample 198-1208A-36X-CC, 5 cm, (34, 35) Sample 198-1208A-36X-CC, 4 cm, (36) Sample 198-1208A-36X-CC, 2 cm. 37–39. Tribrachiatus digitalis (Sample 198-1208A-36X-CC, 8 cm).