64 CALCAREOUS ALGAE OF THE MIDDLE EAST 



borne in the swollen branches. It is easy to see how such an alga, with development 

 of separate reproductive bodies, would resemble certain living genera, e.g. Dasycladus 

 itself, allowing for the very different calcification. 



The Oman Palaeodasycladus-limestone is crowded with examples of the species : 

 presumably they grew in dense patches or thickets like the living Dasycladus. Their 

 ecology is further discussed below. 



Genus PERMOPERPLEXELLA gen. nov. 



Diagnosis. Thin hollow calcified elongate claviform dasyclad ; walls showing 

 consecutive horizontal verticils of large cylindrical branches, rounded in cross- 

 section, pores (branches) of adjacent verticils set alternately, all pores separated by 

 narrow interstices ; proximal and distal terminal openings to thallus. 



Horizon. Permian of Iraq. 



Type Species. Permoplexella attenuata sp. nov. 



Permoperplexella attenuata sp. nov. 



(PI. 17, figs. 1-5) 



Description. Hollow elongate calcified club-shaped thallus, length about 2-5 

 mm., external diameter increasing gradually from 0-5 mm. near the base and 

 swelling to 0-9 mm. or more sub-terminally, internal diameters 45-46% external, 

 ends rounded, terminal apertures of about 0-156 mm. and 0-312 mm. diameter 

 respectively. About 22 consecutive verticils each of about 20 branches, branches in 

 successive verticils arranged alternately. The branches in vertical section are seen 

 to communicate with the internal cavity by a narrow pore, and expand at once to a 

 rounded rectangular section, occasionally seen as flask-shaped in the terminal 

 expansion of the thallus. In cross-section they are rounded-polygonal, about o-i 

 mm. diameter, and separated by calcareous interstices of 0-020 mm. or less. Traces 

 of a narrow longitudinal calcified structure within the central cavity. 



Horizon. Permian of Iraqi Kurdistan. 



Holotype. The specimen figured in PI. 17 fig. 4, from the Permian Zinnar 

 Formation ; Ora, Mosul Liwa, Iraq. V. 52085. 



Paratypes. The specimens figured in pi. 13 figs. 1-3, 5 ; same locality and 

 horizon. V. 52084, 52085. 



Other Material. Random sections in the same samples. 



Remarks. The little dasyclad described above, although distinctive enough in 

 the Iraqi Permian flora studied, shows a combination of characters which are not 

 themselves intrinsically distinctive. The pores (side-branches of the verticils) are 

 simple and do not consistently show any of the shapes characteristic of the different 

 genera of the diploporeae — Diplopora, Gyroporella, Physoporella, etc. Although the 

 thallus is that of the conventional single dasyclad, the terminal apertures suggest 

 that it may possibly be a unit of a serial plant ; for whilst it is true that in some of 

 the more elaborate dasyclads of later geological periods the distal aperture is occupied 



