CALCAREOUS ALGAE OF THE MIDDLE EAST 55 



Ranges) : abundant over this range in much of the material from the sampled 

 surface sections of Ora and Harur, Mosul Liwa, and also from subsurface Upper 

 Permian in Atshan no. 1 well, in the south of Mosul Liwa (see Hudson 1958 ; 

 Dunnington, Wetzel & Morton 1959). Elsewhere in the Middle East Permian 

 recorded by Kuhn (1933) from Iran, by Bilgiitay (1959) and Giivenc (1965) from 

 Turkey and by Rezak (1959b) from Saudi Arabia. 



Remarks. Mizzia velebitana is a characteristic Permian microfossil of circum- 

 global distribution : central and southeastern Europe and north Africa, the Middle 

 East, Sumatra and Japan, and the southwestern United States. Its distribution 

 was plotted and compared by Pia (1937) with that of the living warm-water codiacid 

 alga Halimeda tuna Lmx. Extensive bibliographies of these occurrences have been 

 given by Pia (1937), Johnson & Dorr (1942) and Rezak (1959b) : that given above 

 refers mostly to the Middle East occurrencies. 



Rezak {op. cit.) has discussed the genus and type-species in detail, and given 

 revised diagnoses for them. That for the genus is quoted above in full : the 

 description given here is based on the material from Iraqi Kurdistan studied by 

 me. When compared with the equivalent species-diagnosis of Rezak, which was 

 a synthesis of previous records and his own study of Saudi Arabian material, it is 

 seen that the Iraqi specimens do not attain the maximum size (length breadth and 

 pore-diameter) quoted for the species elsewhere, but are larger in size and equal in 

 pore-diameter to the Saudi Arabian specimens. 



Rezak transferred Mizzia to the dasyclad tribe Diploporeae, after clear demonstra- 

 tion of the regular arrangement of the side-branches : I agree with this. All 

 previous workers have followed Schubert (1908 : 383) in supposing the stem-cell in 

 each globular Mu^'a-segment to have filled the central cavity, so that the primitive 

 unbranched side-branches commenced approximately where the inner calcareous 

 wall is seen in the fossil (e.g. Pia 1920 : 21 ; Rezak 1959 : 534). Theoretically it is 

 possible that a thinner central stem-cell gave rise to thin radiating branches which 

 thickened terminally and were calcified only around the thicker peripheral portions : 

 a comparable arrangement exists in the Recent Bornetella. Although this is a much 

 more complex dasyclad than the Permian Mizzia is believed to have been, it was the 

 comparison-genus used by Wood (1943) in reconstructing the non-calcified parts of 

 the still older dasyclad Koninckopora from the Carboniferous. However, the serial 

 arrangement of connected Mizzia-segments (a phenomenon known from occasional 

 short strings of consecutive fossil segments from various localities, though not yet 

 from Iraq) is believed to indicate a jointed plant somewhat like the living Cymopolia 

 (Pia 1920 ; Rezak 1959b). Mechanically, the 5om£te//fl-interpretation would result 

 in segments which would probably be extremely fragile for the assumed mode of life 

 of Mizzia, even in quiet waters : Bornetella itself is a single non-segmented dasyclad, 

 attached by a short holdfast. It therefore seems more likely, though not definitely 

 known, that the older interpretation is correct. Taken in conjunction with the 

 abundance of the fossil segments and their wide distribution, this would make 

 Mizzia a common dasyclad of primitive structure, vigorous growth, and thick juicy 

 stem-cell. This is consistent with the picture set out in the section on ecology. 



