142 
to faintly pustulose. A narrow but prominent median carina is 
developed on the mainstem and lateral branches, and distinct nodes 
are regularly spaced on the carina at distances equal to the 
interapertural spacing. 
Autozooecial apertures are small, circular, and lack peristomial 
rims. They are regularly spaced (about twice their diameter apart) 
and are usually alternately arranged in two longitudinal rows on 
either side of the median carina, but may occasionally may be paired 
across the carina. The outer margins of autozooecial apertures 
protrude slightly beyond the lateral margin of branches, producing a 
gently sinuous branch outline. Internally the chambers are pentago- 
nal in transverse section and longitudinally rectangular. Hemisepta 
are not developed. 
DISCUSSION. A complete systematic description of D. tenella is 
given in Wyse Jackson, 1988. 
Genus ICHTHYORACHIS M ‘Coy, 1844 
TYPE SPECIES. Ichthyorachis newenhami M‘Coy, 1844, by 
monotypy, from the Lower Carboniferous (Viséan, Chadian?) of 
Killmallock, County Limerick, Ireland. 
M‘coy’S ORIGINAL DIAGNOSIS. ‘Coral plumose, composed of a 
straight, central stem or midrib, having on either side a row of short, 
simple branches or pinnae, all in the same plane; obverse both of the 
midrib and lateral branches rounded, without keel, and each bearing 
several rows of small, prominent, oval pores, arranged in quincunx; 
reverse rounded, smooth or finely striated.’ 
EMENDED DiAGNosis. Acanthocladiid with pinnate zoarium 
composed of a mainstem and regularly-spaced, co-planar lateral 
branches which diverge from the mainstem at a high angle. 
Dissepiments are absent. Branches are circular to sub-circular in 
cross-section. Interapertural areas and the branch reverse surface are 
smooth or faintly striated. Autozooecia are arranged in 4 to 6 
longitudinal rows on the mainstem, and in 3 to 4 rows on lateral 
branches. Autozooecial apertures are small, circular to oval in shape, 
regularly-spaced, and occur on the obverse surface only. 
STRATIGRAPHICAL RANGE. Lower Devonian—Lower Carbonifer- 
ous. 
DISTRIBUTION. British Isles, Europe, United States. 
Ichthyorachis newenhami M‘Coy, 1844 
Figs 42b, 46-47, 51 
v1844 Ichthyorachis newenhami M‘Coy: 205, pl.29, fig.8. 
1854b Ichthyorachis newenhami M‘Coy; M*Coy: 104. 
1857. Ichthyorachis newenhami M‘Coy; Jukes: 454. 
1862 Icthyorachis [sic] newenhami M‘Coy; M ‘Coy, pl.29, fig.8. 
1883 Ichthyorachis sp. Vine: 171. 
1884a Ichthyorachis newenhami M‘Coy; Vine: 196. 
1886 Ichthyorhachis [sic|nevenhami[sic] M‘Coy; Hoernes: 230, 
fig. 233. 
1953 Ichthyorachis newenhami M‘Coy; Bassler: G128, fig. 88 
(3a-c). 
1966v Penniretepora triserialis Owen: 141, pl.9, figs A-C pro 
parte. 
LECTOTYPE. Herein designated NMING:F6044; Kilmallock, 
County Limerick (Viséan, Chadian?); C.B. Newenham Collection; 
figured M‘Coy 1844, pl.29, fig.8. This is the only extant specimen of 
Ichthyorachis from the collection on which M‘Coy based his de- 
P.N. WYSE JACKSON 
scription. Newenham also collected specimens from County Cork 
(M‘Coy 1844: 206). 
MATERIAL. BMNH PD9581-9590, TCD.34052, Upper part of the 
Glencar Limestone (Viséan, Asbian), Carrick Lough, County Fer- 
managh. } 
M‘COY’S ORIGINAL DIAGNOSIS. ‘Stem and lateral branches with} 
five rows of oval, prominent pores, closely arranged in quincunx; - 
reverse flattened, slightly convex, divided by a deep groove along}: 
the middle; obsoletely striated longitudinally; lateral branches half} 
the thickness of the midrib, space between them equal to the)}) 
diameter of the midrib.’ 
EMENDED DIAGNOSIS. Ichthyorachis with small delicate pinnate). 
zoaria. Two sets of straight lateral branches diverge from either side} 
of a thin, straight central main stem at a high angle. Lateral branches 
are regularly spaced and may be offset from each other either side of, 
the main stem, but more frequently occur paired. Branches are }_ 
circular to subcircular in cross-section. The obverse surface is} 
smooth and rounded, with faint longitudinal striae in interapertural) 
areas. The reverse surface is barren, rounded or slightly flattened: 
smooth, longitudinally striated, or with a central groove occurring }_ 
down the centre. Autozooecia are arranged in longitudinal rows 0 
branches with 4 to 5 on the main stem and 3 to 4 on laterals. 
Autozooecial apertures are small, circular to oval in shape, lack 
peristomes, and are regularly arranged in quincunx. | 
DESCRIPTION. Zoaria form small pinnate expansions, consisting }/ 
of a main stem and lateral branches. The largest fragment in the } 
County Fermanagh assemblage examined is 17.3 mm in length (the | 
lectotype, which was collected in County Limerick, is larger, anc 
measures 53 mm in length (Fig. 47)). The main stem is thin, straighi 
or gently flexuous, and circular in cross-section. A small increase it 
main stem diameter precedes lateral branch development. Lateral}: 
branches lie in the same plane as the mainstem, and branch from i)}¥ 
at angles of between 50° and 60°. They are regularly spaced, abou! j= 
2 diameters apart, and usually paired either side of the main stem 
7 
fe 
than the mainstem with a straight or undulatory margin, and / 
circular cross-section. The longest lateral branch observed is only 1) 
mm in length: most are broken at their bases. The obverse surface 1 }= 
rounded and faint longitudinal striae are developed along its lengt }_ 
The reverse surface is also rounded, and may bear indistinct longit ; 
dinal ridges or be smooth. 7 
.- = 
eters apart. Apertural spacing becomes fractionally closer towards’ 
branch node. 
Details of internal features are unknown as only silicified fraj 
ments have been recovered from Carrick Lough. 
Discussion. Although only 10 colonies of Ichthyorachis newe }\, 
hami were measured it was found that they showed very lit| }, 
