Figs 19-24 Rhombopora cylindrica sp. nov.; 19-23, Upper part of the Glencar Limestone (Viséan, Asbian), Carrick Lough, County Fermanagh; 19, 
BMNH PD9509 (paratype), colony form showing long straight branches, with interconnected longitudinal and oblique rows of autozooecia, x20; 20, 
BMNH PD9507 (holotype); 20a, zoarial fragment with distal growing tip, showing regular arrangement of autozooecial apertures around branch; large 
acanthostyles are situated at the proximal and distal ends of apertures with smaller heterostyles developed on surrounding walls, x20; 20b, detail of 20a 
showing autozooecial apertures and acanthostyles on interapertural walls, x110; 21, BMNH PD9534 (paratype), transverse section showing radial 
budding pattern of autozooecia and the differentiation of endozone and exozone; 22, BMNH PD9532 (paratype), tangential section showing oval-shaped 
autozooecia and heterostyles (C-type stylets) developed on interapertural walls, x100; 23, BMNH PD9531, (paratype), longitudinal section showing 
autozooecial chamber shape and the thickened exozonal walls, x40; 24; Shales above Main Limestone, Pendleian, Upper Carboniferous, Hurst, near 
Richmond, Yorkshire, U.K. TCD.41515; 24a, longitudinal section, x25; 24b, detail of 24a showing morphology of acanthostyles, x80. 
at low angles of 10° to 25° and chambers are eight times as long as 
their maximum width. The chamber bends through 30° to 40° at the 
endozone/exozone boundary and vestibules are orientated at an 
angle of 45° to the zoarial surface. In cross-section chambers are 
rhombic, pentagonal or subcircular in shape. Chamber walls are thin 
(0.01—0.03 mm), compound (a very thin granular core covered by 
laminated skeleton) in the endozone and thicker, with a predomi- 
nantly laminated skeleton, in the narrow exozone region. The exozone 
varies in width between 0.1 and 0.2 mm and is approximately one 
fifth the width of branches. Thin terminal diaphragms may be 
present. 
Autozooecial apertures are large to moderate in size, oval to 
circular in shape, regularly spaced approximately one diameter 
apart, and spirally arranged in quincunx in 10 to 16 longitudinal 
rows around branches. 3 to 6 apertures occur longitudinally and 8 taj), 
10 diagonally along a 2mm line. Autozooecial apertural size is) 
constant on a zoarium except at branch nodes. The first autozooecial 
apertures on new branches are long and thin, particularly on the 
reverse surface of branches. Uniformity of size is regained 4 to * 
apertures along branches. Metapores are rare. They are small (0.01- 
0.13 x 0.02-0.10mm), irregular in shape and one or occasionally 
two are found proximal of autozooecial apertures, with other: 
sparsely distributed elsewhere on interapertural walls. They at 
usually developed close to branch divisions and zoarial thickening’ 
They originate within the exozone. 
Stylets are numerous and structurally varied. They occur in one 0 
two rows, between autozooecial apertures. One or rarely twi 
acanthostyles (up to 0.07mm wide) occur at autozooecial apices 0) 
in 
w 
