94 CALCAREOUS ALGAE OF THE MIDDLE EAST 



ciently numerous to prove the continued growth of Mizzia and other dasyclads in 

 coastal environments throughout the whole period of deposition, even though the 

 sediments at the sampled successions of Harur and Ora reflect the intermittent 

 shifting of this coastline. The minor dasyclad elements, Anthracoporella, Atradyli- 

 opsis, Clypeina, Permoperplexella, Pseudoepimastopora and Pseudoverniiporella do not 

 in any way conflict with the picture drawn from the dominant Mizzia. The very 

 scarce Clypeina occurs at the top of the Zinnar and the bottom of the Satina Evapor- 

 ite, a fact consonant with later opinions on the facies behaviour of the Mesozoic 

 species. 



Rezak (1959) dealing with the Saudi Arabian Permian, observed the occurrence- 

 relationships and associations of Epimastopora, Gymnocodium and Mizzia, and 

 suggested a possible algal depth zonation as explanation. In Iraq Pseudoepimasto- 

 pora is confined to the lowest division, the Zinnar Formation, in which particularly 

 well-marked coral and brachiopod beds occur and in which the Gymnocodium- 

 Mizzia beds are more sporadic than in the later beds. From the sampling available 

 to me, I cannot interpret my records along the lines of Rezak's suggestion, but such 

 depth-zonation may well have existed. 



The rarity of Triassic dasyclads in the Middle East has already been noted ; it 

 forms a remarkable contrast to the diplopore-limestone of alpine Europe. The 

 evidence of the Kurdistan Geli Khana and Kurra Chine formations (Middle and 

 Upper Trias) suggests originally unfavourable conditions. 



Two Jurassic algal occurrences give a clear picture of the original ecology. The 

 Palaeodasycladus-bed in the Liassic portion of the Musandam Formation in peninsular 

 Oman, Arabia, shows a limestone, now partially dolomitized, crowded with healthy, 

 full-grown specimens of well-developed P. mediterraneus, whole and broken. Asso- 

 ciated are concentric nodules of probable cyanophyte algal origin. The picture is of 

 an extensive spread of the dasyclads in clear, shallow warm water, on a limy bottom : 

 a typical habitat. 



In the Upper Jurassic of Qatar and elsewhere in the Persian Gulf area the " Arab 

 zone " (Kimmeridgian-Tithonian) yields a florule of Clypeina jurassica, Salpingopor- 

 ella annulata and Cylindroporella arabica occurring in fine-grained and oolitic lime- 

 stones : associated are numerous crustacean coproliths, Favreina salevensis (Pare^as), 

 and small gastropods and foraminifera. The picture is again of shallow, clear limy- 

 bottomed waters, possibly lagoonal or enclosed ; the snails and crustacean traces 

 may be indirect evidence of an abundant growth of non-calcarous green algae of 

 which nothing certain now remains. The modern eel-grass beds of the West Indies 

 and Bahamas would be comparable : Chapman (1961 : 9) gave a Jamaican record 

 of numerous Codiaceae and Dasycladus sp. from this environment. 



In the same general area of southeastern Arabia a very different picture is given by 

 the Lower Cretaceous algal beds penetrated in the Fahud no. 1 boring. Here the 

 rock is formed of rounded pieces of the crusting problematic algae Lithocodium and 

 Pycnoporidium, with similar-sized pieces of stromatoporoids and less frequent coral, 

 and rare valves of cemented thecidean brachiopods. Associated are numerous 

 examples of segments of the dasyclad Cylindroporella sugdeni. This is reef or shoal 



