LOWER CARBONIFEROUS BRYOZOA 
149 
‘rapidly at the endozone/exozone boundary, and wall thickness re- 
‘mains constant (mean thickness 0.07mm) throughout most of the 
‘exozone. Thin basal diaphragms are infrequently developed in the 
endozone, whereas very thin diaphragms are occasionally devel- 
oped in the exozone. 
4 Autozooecial apertures are of moderate size, circular in shape, 
‘and are closely packed, approximately their own diameter apart. 
Interapertural areas are irregular in width. Exilazooecia are very 
bundant between autozooecia and vary greatly in shape and size. 
‘They are usually circular to oval, but in interapertural angles small 
bentagonal forms occur (0.02—0.1mm in diameter). Frequently, one 
pr two exilazooecia are located between autozooecia. Exilazooecia 
inate within the exozone where they form short, narrow tubes. 
“Maculae, 0.4mm in diameter, occur occasionally and comprise 
Seistcrs of exilazooecia. 
Acanthostyles are abundant in interapertural walls. Relatively 
arge acanthostyles (mean diameter 0.03mm) persist at interapertural 
ngles around autozooecia while smaller acanthostyles (mean 
‘Table 23 Measurements of Dyscritella miliaria (in mm). N=5. 
'D 19 4.59 3.17 6.15 9.65 5.06 
4 21 16.06 9 DD) 28.53 451 
2 25 8.35 7 10 10.16 147.80 
AD 30 0.12 0.09 0.22 12.08 5.34 
WT 30 0.08 0.03 0.28 38.77 2.30 
oD 30 0.04 0.02 0.10 31.90 4.04 
NT 9 2.64 1.91 3.52 13.47 5.50 
18 0.97 0.57 1.38 8.00 1.24 
Figs 63-65 Dyscritella miliaria (Nicholson, 1881); 63, Upper part of the Glencar Limestone (Viséan, Asbian), Sillees River, County Fermanagh; BELUM 
) K3442; 63a, large zoarial fragments showing ramose growth-form and large circular autozooecial apertures surrounded by irregularly-placed 
exilazooecia, x1; 63b, detail of 63a, x15; 63c, cross-section showing autozooecial chambers with thickened exozonal walls, x50: 63d, detail of 63c, 
| showing exilazooecium developed in exozone between adjacent autozooecial apertures, x120; 64-65, Carboniferous shales (probably Redesdale 
Ironstone Shale (Asbian), Lower Limestone Group), Redesdale, Northumberland; 64, AUGD.10135a (lectotype), ramose branching zoarial fragment 
with crowded arrangement of autozooecial apertures surrounded by much smaller circular or irregularly-shaped exilazooecial apertures, x5; 65, GSM 
1967.66.384 (paralectotype), tangential section showing oval autozooecial apertures surrounded by numerous exilazooecia, x15. 
diameter 0.01mm) are developed in a line on interapertural walls 
between both autozooecia and exilazooecia. 
DISCUSSION. This is the first reported occurrence of the trepostome 
Dyscritella miliaria from the Carboniferous of Ireland. The abun- 
dance of exilazooecia (“interstitial tubuli’ of Nicholson, 1881) makes 
the taxon very distinctive. It was first described, as Monticulipora 
tumida var. miliaria, from the Lower Carboniferous of England 
(Nicholson 1881). Subsequent specimens from the Midland Valley 
of Scotland were discovered in the Young Collection at the Hunterian 
Museum (Bancroft 1984). D. miliaria also occurs at Llangollen, 
North Wales, in strata of Asbian age (A.J. Bancroft, pers. comm., 
April 1988). 
Dyscritella miliaria is rare in the Lower Carboniferous of the 
Fig. 66 Dyscritella miliaria (Nicholson, 1881). Line drawing of external 
features of BELUM K3442; scale bar = 0.1 mm. 
