| 41. | Like rugose corals, they lived entirely during the Paleozoic, being found from the Ordovician to the Permian.
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| 42. | The head is rugose, dull rufous orange, marked centrally with a darker brown, inverted V .
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| 43. | With Stromatoporoidea and rugose corals, the tabulate corals are characteristic of the shallow waters of the Silurian and Devonian.
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| 44. | At maturity, the aerial hyphae of this species differentiates into tight, spiral chains of rugose, cylindrical spores.
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| 45. | Its medulla is white, with a chestnut-dark brown coloured underside, being rugose, veined and papillate.
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| 46. | These plants are almost stemless herb with radical glabrous rugose, thick winkled leaves in flat tuffs leaves some 6in long.
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| 47. | The oval leaves are grey-green, long by wide, with a rugose upper surface and whitish hairy underside.
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| 48. | It contains abundant examples of some of the earliest shell beds in the geological record and the earliest rugose corals known.
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| 49. | Rugose or horn corals became dominant by the middle of the Silurian period, and became extinct early in the Triassic period.
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| 50. | Unlike " P . brachydeirus ", its cervical centra possess a rugose ventral surface, but lack ventral keel.
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