82 CALCAREOUS ALGAE OF THE MIDDLE EAST 



divides into four secondaries : in the older, slimmer parts of the thallus this is all the 

 branching seen, but in the later, wider portions each secondary divides into four 

 tertiaries which reach the exterior as pores. 



Horizon. Palaeocene-Lower Eocene of Iraqi Kurdistan. 



Material. From the Kolosh Formation (Palaeocene-Lower Eocene) of Surdash, 

 Sulemania Liwa ; Koi Sanjak, Erbil Liwa, and Sundur, Mosul Liwa : all in northern 

 Iraq. 



Remarks. Trinocladus perplexus is the almost invariable companion of the 

 codiacid Ovulites morelleti Elliott in the clastic facies or Kolosh green-rock sands of 

 Kurdistan, where occurrences of the two species far outnumber occasional records of 

 other algae. Trinocladus is however missing from the varied, richly algal Sinjar 

 limestone and marl facies of the same age-range, where 0. morelleti is also abundant. 

 This ecological distribution is considered elsewhere in this work. 



T. perplexus has not been seen outside this limited area ; its distribution is thus 

 very different from that of the related Thyrsoporella silvestrii, or indeed from the 

 older species Trinocladus tripolitanus. 



Trinocladus radoicicae sp. nov. 

 (PI. 24, fig. 8) 



Description. Tubular cylindrical calcified dasyclad, probably originally slender 

 club-shaped. Length unknown, fragments up to i-o mm. seen ; maximum observed 

 diameter 075 mm. d/D ratio about 33%. Smaller transverse sections of 0-42 mm. 

 and 0-34 mm. diameters show a verticil of seven branches : the primaries swell out 

 markedly before dividing into thinner secondaries (probably four) and these in turn 

 into several tertiaries. Specimens of smaller diameter show only primaries and 

 secondaries. 



Horizon. Maestrichtian of Iraqi Kurdistan and (subsurface) Dukhan, Arabia. 



Syntypes. The specimens figured in PI. 24, fig. 8 from the Tanjero Clastic 

 Formation (Maestrichtian) of Diza, Erbil Liwa, Iraq. V. 521 16. 



Other Material. Several random thin-sections from the same formation and 

 horizon, Diza, Erbil Liwa, and Balambo, Sulemania Liwa, Iraq. Also similarly 

 from the subsurface top Aruma of Dukhan no. 1 well, Qatar, Arabia. 



Remarks. Although the green-rock clastic facies continues in Iraqi Kurdistan 

 from Tanjero Formation (Maestrichtian) to Kolosh Formation (Palaeocene), it 

 contains different species of the codiacid Ovulites, 0. delicatula Elliott and 0. 

 morelleti Elliott respectively. These are presumably successional in evolution. As 

 already remarked, Trinocladus perplexus is the constant companion of 0. morelleti in 

 the Palaeocene ; T. radoicicae is now described as the Maestrichtian associate of 0. 

 delicatula. It is, however, rare and fragmentary when compared with 0. delicatula 

 (itself much less common than 0. morelleti). 



T. radoicicae is similar in form, approximate size and succession of branch- 

 complexity within the one thallus to T. perplexa. It differs noticeably in the form 



