LOWER CARBONIFEROUS BRYOZOA 
Fig. 36 Line drawing of external features of Streblotrypa pectinata 
Owen, 1966 (BMNH PD9565); a, colony form, scale bar = | mm; b, 
detail of autozooecial apertures surrounded by metapores, scale bar = 
0.1 mm. 
No complete colonies were observed; the largest fragment examined 
measured 10.2mm in length. Branches bifurcate at irregular inter- 
vals, and lateral ramifications diverge at a high angle of between 83° 
nd 90°. Branches retain a constant width between ramifications and 
there is only a slight increase just prior to and after branching. 
Autozooecial apertures are moderate in size (0.08-0.19 by 0.05— 
).10mm), oval in shape, evenly spaced 2 to 2.5 diameters apart, and 
pecur in 12 to 20 longitudinal rows around the entire branch. Within 
‘any one Zoarial fragment apertures are of approximately constant 
dimension. Small oval to occasionally circular-shaped metapores 
€ abundant; twelve to twenty occur in 3 to 4 longitudinal rows 
petween the distal and proximal extremities of adjacent autozooecial 
‘Apertures, and beyond the lateral margins either a single or double 
ow of metapores is present. In cross-section metapores have a thin 
eck and flare towards the endozone. They are approximately 
-).09mm deep; only a small proportion of metapores penetrate to the 
ase of the exozone. 
| Autozooecia are budded from an axial region in which axial 
fooecia are not present. Chambers are initally recumbent in the 
‘tndozone and diverge from the branch axis at a low angle of less than 
'}5°. At the exozone they bend through 65° to become orientated 
early perpendicular to the zoarial surface. From this surface the 
yroximal wall of the vestibule slopes at a moderate angle, while the 
jistal wall is perpendicular (Fig. 35a). In cross-section chambers are 
entagonal and slightly inflated laterally. Chamber walls in the 
jndozone are thin (0.01mm) and composed of a granular core 
overed with very thin laminated layers. The walls thicken rapidly 
trazooidaly (up to 0.4mm) in the exozone; much of this expansion 
due to metapore development. 
Acanthostyles are small (0.02-0.05mm in diameter) and blunt 
nd are randomly distributed in interapertural areas where they lie at 
€ proximal end of metapores. Acanthostyles arise at the endozone/ 
ozone boundary, thicken slightly laterally and have solid cores 
mposed of granular skeleton, around which is bent laminated 
eleton. They form dark granular circles on the zoarial surface. 
ble 14. Measurements of Streblotrypa pectinata in mm. N=13. 
137 
DISCUSSION. Streblotrypa pectinata is very rare in the Lower 
Carboniferous of the British Isles. From the limestones of County 
Fermanagh less than 20 zoarial fragments and a small number of 
specimens in section were found. 
The presence of metapores, small acanthostyles, and a thin exozone 
make this bryozoan very distinctive. Only three other species of Streb- 
lotrypa have been described from strata of Carboniferous age in the 
British Isles: Streblotrypacortacea(Owen 1966), Streblotrypaminuta 
(Vine 1889), and Streblotrypa nicklesi (Ulrich in Vine 1884b).S. pect- 
inatadiffers fromS. cortacea which possesses athick exozone and few 
metapores; S. minuta, in which sharp longitudinal ridges and a small 
number (6 to 8) of metapores are developed; and. nicklesi, which has 
9 to 15 metapores and 12 longitudinal rows of autozooecial apertures. 
STRATIGRAPHICAL RANGE. Lower Carboniferous (Asbian). 
DISTRIBUTION. Apart from the occurrences at Carrick Lough and 
Sillees River, County Fermanagh Streblotrypa pectinata has previ- 
ously only been recorded from Castleton, Derbyshire (the type 
locality). 
Genus CLAUSOTRYFPA Bassler, 1929 
TYPE SPECIES. Clausotrypa separata Bassler, 1929 by original 
designation from the Permian of Timor. 
DISCUSSION. The taxon has both trepostome and cryptostome 
features. Of the former the long autozooecial chambers, moderately 
thick exozone, many acanthostyles particularly associated with 
autozooecial apertures. The dendroid zoarial form, arrangement of 
autozooecial apertures and the presence of metapores strongly 
Suggest cryptostome affinities. I consider Clausotrypa to have 
stronger cryptostome than trepostome affinities. 
Bassler (1929) assigned the genus to the Order Cryptostomata, 
family Rhabdomesidae. Many Soviet authors have placed it in the 
suborder Rhabdomesina Astrova & Morozova, 1956 (Romantchuk 
1970, Morozova 1970, 1981), while others assign the genus to the 
suborder Streblotrypina Gorjunova, 1985 (Gorjunova 1985). Blake 
(1983: 592) does not consider Clausotrypa to be a rhabdomesonid, 
while Gorjunova (1985) does. Blake & Snyder (1987) show, based 
on a cluster analysis of 44 characters, that Clausotrypa is rather 
unusual. It does not easily fall into any familial grouping. 
Recognising the obvious need for fuller taxonomic and compara- 
tive studies the genus is tentatively placed here in the family 
Hyphasmoporidae, Vine 1885. 
Clausotrypa ramosa (Owen, 1973) comb. noy. Figs 37-41 
v1973 Sulcoretepora? ramosa Owen: 304, pl. 9a—c. 
HOLOTYPE. The holotype of Sulcoretepora? ramosa Owen, 1973 
is represented by a zoarial fragment and three thin sections cut from 
it, collected from shales below the Rossmore Mudstone (upper 
Viséan), Tullaghoge, County Tyrone, in the collections of the Ulster 
Museum (BELUM K1830). 
MATERIAL. BMNH PD9577; 9627-9637; 9730-9739:TCD.34067- 
34078, 34136, 34163, Upper part of the Glencar Limestone (Viséan, 
Asbian), Carrick Lough, County Fermanagh. TCD.42513, 42531- 
42534, Upper part of the Glencar Limestone (Viséan, Asbian), 
Sillees River, County Fermanagh. 
DIAGNOSIS. Clausotrypa forming semi-robust erect cylindrical 
dichotomising zoaria. Autozooecia more frequent on one side of 
branch than the other. Metapores, closed to the surface, are devel- 
oped in interapertural areas. Autozooecial apertures are circular, 
moderate in size, widely spaced, and are surrounded by six to eight 
