8o CALCAREOUS ALGAE OF THE MIDDLE EAST 



(observed) up to 3-5 mm., external diameter up to 078 mm., internal diameter from 

 33-50%, figures in the lower half of this range being most common ; verticils of 

 horizontal branches close-set, about 9 per mm. of tube-length, with six or more 

 branches per verticil. Each primary branch is considerably wider than high, and in 

 transverse section is markedly swollen with curved sides : a thin vertical partition 

 marks the beginning of division into two secondaries, smaller but similarly swollen, 

 and these in turn each divide into four little swollen tertiaries. These each divide 

 into several terminal branchlets, probably four, which reach the outer surface as 

 pores. On a specimen of 0754 mm. external diameter the maximum branch- 

 diameters in transverse section were primary, 0-156 mm. ; secondary 0-117 mm., 

 tertiary 0-039 mm -> and quaternary, about 0-015 mm. 



Horizon. Uncommon in Palaeocene-Lower Eocene of Middle East, but common 

 in the Middle Eocene of the same area. Listed by Pfender (1940) from the Eocene 

 of Madagascar. 



Material. In Iraq, seen from the Palaeocene-Lower Eocene Kolosh Formation 

 of Sedelan, Sulemania Liwa, and from the Palaeocene of the Ghurra scarp, west- 

 southwest of Wagsa, Diwaniyah Liwa. In Arabia, from the Palaeocene-Lower 

 Eocene of Sahil Maleh, Batinah Coast, Oman, and from the Palaeocene of Aqabar 

 Khmer, Hajer, Hadhramaut. See also Hadhramaut record of Beydoun (i960 : 

 146). (The much more abundant Middle Eocene occurrences are discussed below : 

 one of Pfender's records, however, is from the Palaeocene of Turkey.) 



Remarks. Thyrsoporella silvestrii Pfender was described from Egyptian Middle 

 Eocene material and compared with the European Thyrsoporella cancellata Gumbel 

 from the French Middle Eocene. This latter (L. & J. Morellet 1913) is a longer, 

 thinner, more fragile species, with a proportionally wider stem-cell (66% of external 

 diameter). Pfender recorded her species from the Middle Eocene of Egypt and 

 Somalia, and also from Syria, Turkey and Madagascar. In the collections now 

 studied it has been seen commonly in the Middle Eocene of north and south Iraq, and 

 of Oman. 



In the Palaeocene-Lower Eocene occurrences studied for this work the species is 

 rare. The records are all based on random sections, and it is possible that with a 

 good series of specimens these older records might prove to be of a species or variety 

 distinguishable from Pfender's species : this has not been possible so far. Pfender 

 (1940) did not illustrate her paper, though this was remedied by Massieux (1966), and 

 the Morellets worked on dissections of solid specimens from the French Eocene. The 

 opportunity is now taken to illustrate Thyrsoporella silvestrii by figuring some good 

 thin-sections of Arabian (Oman) material from the Middle Eocene. 



Genus TRINOCLADUS Raineri 1922 



Diagnosis. Calcified tubular dasyclad showing successive verticils of radial 

 branches, each branch showing outwardly-widening primaries giving rise to several 

 similar-shaped secondaries, and these in turn to bunches of tertiaries : branches of 

 the lower verticils may not show the full detail. Branches not alternate in position 

 from verticil to verticil. 



