WESTERN AUSTRALIAN PERMIAN BRACHIOPODS 
9 
Cyrtella koopi sp. nov. 
Fig. 5A-E 
Pseudosyrinx sp. afF. nagmargensis (Bion).— 
Thomas in Dickins 1976: 99. 
Etymology. Named after W. J. Koop, collector of the 
holotype. 
Holotype. CPC 28046, an internal mould of a con¬ 
joined shell from locality TK5A, Scott Bluff. 
Diagnosis. Large, wide species with wide, rela¬ 
tively deep sulcus; dorsal fastigium apparently 
grooved posteriorly but flat anteriorly; ventral 
adminicula short; 9 to 10 broadly rounded, 
coarse costae on each flank. 
Description. Internal mould large, transverse 
(estimated 100 mm wide). Anterior commissure 
sinuous with prominent fold. Ventral valve 
massively thickened posteriorly (ventral inter- 
area of unknown height). Dorsal valve not thick¬ 
ened greatly; external ornament clearly defined 
on interior. Sulcus deeply rounded, extended 
into prominent ventral tongue. Ventral external 
ornament poorly impressed on anterior of valve 
interior. Costae apparently coarse, low and 
gently rounded; number not clear. 
Dental plates stout with blunt thick teeth and 
short thickened adminicula. Ventral muscle 
field prominent (20 mm wide, 25 mm long); 
diductor muscle scars longitudinally striate 
anteriorly, radially striate posteriorly; adductor 
muscle scar essentially smooth. Posterior part of 
muscle field bisected by apical callus. Interior of 
ventral valve either side of muscle field deeply 
pitted; remainder of valve interior smooth. 
Dorsal interior with prominent fastigium, 
flattened anteriorly but possibly with groove 
posteriorly. Flanks of valve with up to 10 broad, 
flattened costae (up to 3 mm wide at anterior of 
valve). Cardinal process relatively small (5 mm 
wide); socket plates stout. Thin dorsal septum 
arises 3 mm anteriorly of cardinal process, 
extends approximately two-thirds of valve 
length (25 mm). Minute pustules scattered on 
mould surface indicate punctate shell. 
Discussion. Although based on only one internal 
mould, the new species is named in view of the 
distinctive nature of the fastigium and the rela¬ 
tively coarse costae. Cyrtella australis Thomas 
(1971) from the Lyons Group and Callytharra 
Formation has finer, more numerous costae 
than the new species and a distinct dorsal groove 
on the fastigium. Cyrtella nagmargensis (Bion, 
1928; see also Reed, 1932) is characterised by 10 
to 15 internal costae and a distinct furrow on the 
fastigium. Specimens of C. nagmargensis from 
the Sakmarian of Afghanistan (Termier et al. 
1974) are comparable with those from Kashmir, 
but specimens attributed to this species from the 
Sakmarian of Tibet (Yang & Fan 1983, pi. 3, figs 
2-5; Hu 1983. pi. 3, figs 17-23; Jin 1985, pi. 1, 
fig. 23) possess finer, sharper and more numer¬ 
ous costae than C. koopi. 
Cyrtella kulikiana (Fredericks, 1916; see also 
Ifanova 1972) is a large species from the 
Artinskian and Kungurian of Northern Euro¬ 
pean Russia and possesses more numerous cos¬ 
tae than the new species. 
Genus Myodelthyrium Thomas, 1986 
Type species. Pseudosyringothvris dickinsi Thomas, 
1971 
Myodelthyrium dickinsi (Thomas, 1971) 
cf. Pseudosyrinx sp. nov.—Dickins & Thomas 1956: 
52. 
Pseudosvrinx sp. nov.—Thomas in Dickins 1961: 
288. 
Pseudosyringothyris dickinsi Thomas 1971: 140, 
pi. 10, figs 1-5, pi. 11, figs 1, 2, pi. 12, figs 1-4, pi. 13, 
fig. 3, pi. 29, fig. 7. 
Comments. Thomas (1971, pi. 13, fig. 3a, b) fig¬ 
ured an external mould of a ventral interarea 
(CPC 1643) from the Cuncudgerie Sandstone in 
Well 27, in the southern central part of the Can¬ 
ning Basin (22°49'S, 123°40'E). No new material 
of this species is available from the Cuncudgerie 
Sandstone. 
Superfamily Spiriferacea King, 1846 
Family Spiriferidae King, 1846 
Subfamily Trigonotretinae Schuchert, 1893 
Genus Trigonotreta Koenig, 1825 
Type species. Trigonotreta stokesii Koenig, 1825 
Discussion. The relationship of Trigonotreta to 
Neospirifer and the reasons for assigning various 
Western Australian spiriferid species to Tri¬ 
gonotreta have been discussed by Archbold & 
Thomas (1984b, 1986). 
