| 
LOWER CARBONIFEROUS BRYOZOA 
| morphological variation. Main stem width, lateral branch width, 
_ lateral branch spacing, and autozooecial apertural diameter all dis- 
play low coefficients of variation, both within and between colonies. 
| A slightly larger variation occurs in autozooecial apertural spacing. 
j Ichthyorachis newenhami is a distinctive but uncommon fenestrate 
_ form found in the Carboniferous of the British Isles. It has previ- 
i ously been reported only from Counties Cork and Limerick (M‘Coy 
| 1844), Hook Head in County Wexford (Courceyan) (Dresser 1960), 
and Castleton in Derbyshire (Vine 1883, 1884a). 
Examination of some of the type specimens of Penniretepora 
triserialis Owen, 1966 from the Upper Viséan of Treak Cliff, 
Castleton, Derbyshire (holotype: LL.2978; paratype: LL.2980) shows 
that autozooecia are arranged in three rows on mainstems and in two 
Ichthyorachis, and conceptually cannot be attributed to 
Penniretepora. The gross size of the specimens shows them to lie 
within the range exhibited by /. newenhami. The remaining type 
material of P. triserialis (paratypes: LL.2979, LL.2981-2983), also 
from the Upper Visean of Treak Cliff, Castleton, Derbyshire, has 
been examined and the ‘third row of autozooecia’ on mainstems are 
found to be the cores of abraided carinal nodes. These specimens 
belong to an indeterminate Penniretepora species and P. triserialis 
Owen, 1966 is herein regarded as a species inquirenda. 
| Lower Devonian species of Ichthyorachis are also known. I. 
Vreis occurs in the Helderbergian of New York (Hall 1874), and 
Ichtyorachis [sic] sp. has been found in the Emsian of France 
(Rondeau 1890, Bigey 1973). 
King (1849, 1850) referred Ichthyorachis to his genera 
Acanthocladia and Thamniscus owing to the similarities of the 
branching pattern with the former, and autozooecial arrangement 
with the latter. Comparison of the three taxa shows King’s reasoning 
0 be incorrect. Ichthyorachis is very distinct from the other two 
‘taxa. Branches in both Acanthocladia and Thamniscus are more 
robust and irregular than in Ichthyorachis, and distinct peristomial 
e are developed around autozooecial apertures in Thamniscus. 
1 
Ichthyorachis does, however, resemble Baculopora Wyse Jackson 
1988 in the development of 4 or more rows of autozooecia on 
branches. However, the two taxa are generically distinct in that 
Ichthyorachis bears regular lateral branches on both sides of the 
‘main stem and Baculopora does not. 
' STRATIGRAPHICAL RANGE. 
Asbian). 
| 
_ DISTRIBUTION. 
| 
| Family FENESTELLIDAE King, 1850 
| Genus THAMNISCUS King, 1849 
YPE SPECIES. Keratophytes dubius Schlotheim, 1820 by original 
esignation from the Permian of Germany. 
Lower Carboniferous (Courceyan— 
British Isles. 
Thamniscus colei Wyse Jackson, 1988 Fig. 48 
ATERIAL. BMNH PD8960-8982; TCD.29314-29323, 
CD.34152, 42606b; NMI:F19531-F19540; BELUM K2154, 
| <2157, K2166, K2223, K12118-K12127, Upper part of the Glencar 
i mestone, Viséan (Asbian), Carrick Lough, County Fermanagh. 
_ }MNH PD8959, 8983-8985; TCD.42543-42546, Upper part of the 
- blencar Limestone (Viséan, Asbian), Sillees River, County Ferman- 
gh. 
Boers The zoarium is small and develops from a flared 
_[asal holdfast to an open basket 7mm wide. The heavily calcified 
rows on lateral branches. This arrangement is characteristic of 
; 
143 
holdfast is barren of apertures, whereas apertures open on the outer 
side of the basket. Branches are very robust (1.40 mm maximum 
width), circular in cross-section and bifurcate at irregular intervals at 
a high angle. Branches maintain a constant width along their length, 
and there is no increase in branch width prior to or following 
bifurcation. Branch surfaces are smooth. Autozooecial apertures are 
arranged in two to five sub-linear rows in an irregular pattern on the 
obverse branch surface. The outer peristomial rims of the lateral 
rows of apertures protrude slightly beyond normal branch margins 
giving them an undulatory appearance. Autozooecial apertures are 
circular, large and are surrounded by prominent thin peristomes. 
Autozooecial chambers are elongate, circular in cross-section, and 
narrow proximally. 
Discussion. A complete systematic description of ZT. colei is 
given in Wyse Jackson, 1988. 
Suborder PHYLLOPORININA Lavrentjeva, 1979 
Family CHAINODICTYONIDAE Nickles & Bassler, 1900 
Genus RHOMBOCLADIA Rogers, 1900 
TYPE SPECIES. Rhombocladia delicatula Rogers, 1900 by original 
designation from the Upper Carboniferous of Kansas, U.S.A. 
REVISED DIAGNOSIS. Chainodictyonid with unilaminate, ramose 
zoarium, with dichotomous branches which are oval to elliptical in 
cross-section. Autozooecia are arranged in 4 to 12 longitudinal rows 
on obverse surfaces only. Superior hemisepta well developed; basal 
diaphragms rare. Autozooecial apertures oval. Reverse surface coy- 
ered with thin semi-circular ridges. 
STRATIGRAPHICAL RANGE. Lower Carboniferous—Lower Permian. 
DISTRIBUTION. British Isles, Europe, North America, the CIS 
(former Soviet Union), China. 
49 50 
Fig. 49 Diploporaria marginalis (Young & Young, 1875a). Line drawing 
of external features of BMNH PD9580; scale bar = 1 mm. 
Fig. 50 Ichthyorachis newenhami M‘Coy, 1844. Line drawing of external 
features of BMNH PD9581; scale bar = 1 mm. 
