58 
N. W. ARCHBOLD 
possesses distinct concentric growth interrup¬ 
tions as in Arctitreta plicatilis (Hosking) as de¬ 
scribed by Thomas (1958), but indicates a larger 
species than the Callytharra species. Costellae 
number 8 to 12 per 5 mm and increase predomi¬ 
nantly by intercalation although rare bifurcation 
does occur. Costellae are gently rounded and 
broaden anteriorly, and hence are not flattened 
as in Arctitreta plicatilis but rather resemble 
those of Streptorhynchus crassimurus Thomas, 
1958 from the late Baigendzhinian Noonkanbah 
Formation, Canning Basin. 
Family Orthotetidae Waagen, 1884 
Subfamily Orthotetinae Waagen, 1884 
Genus Permorthotetes Thomas, 1958 
Type species. Permorthotetes callytharrensis Thomas, 
1958. 
Permorthotetes sp. 
Fig. 1A, B, D 
Permorthotetes sp .—Thomas 1958: 107.—Condon 
1962a: 11.—Condon 1967: 102. 
Orthotetacea nov. gen.—Konecki et al. 1958: 33. 
Material. One incomplete mould of a dorsal valve 
(CPC 24503) from locality BMR 7864, 0427, width 
38.5-f mm, length 42+ mm; and one natural cast of a 
ventral valve exterior (CPC 24504) from locality BMR 
WB 9, width 67+ mm, length 42 mm. 
Comments. Two specimens arc consistent with 
the identification of Permorthotetes from the 
basal One Gum Formation. The dorsal valve 
internal mould reveals an uneven convex profile 
and a low median ridge bisecting the muscle 
field. The cardinal process is unknown. The ven¬ 
tral valve external ferruginous cast is large, 
wrinkled, irregularly gently convex posteriorly 
and flat anteriorly. Costellae are fine (about 7 to 
8 per 5 mm at 30 to 40 mm from umbo) and 
increase by intercalation. Intercostal troughs are 
wider than costellae. A comparison with Per¬ 
morthotetes callytharrensis Thomas, 1958 is 
suggested but better material is required for 
detailed comparisons. 
Order Chonetida Nalivkin, 1979 
Suborder Chonetidina Muir-Wood, 1955 
Superfamily Chonetacea Bronn, 1862 
Family Rugosochonetidae 
Muir-Wood, 1962 
Subfamily Rugosochonetinae 
Muir-Wood, 1962 
Genus Neochonetes Muir-Wood, 1962 
Subgenus Neochonetes (Sommeriella) 
Archbold, 1982 
Type species. Chonetes prattii Davidson, 1859. 
Comments. The subgeneric name Sommeria 
Archbold. 1981 was replaced by the name Som¬ 
meriella by Archbold, 1982. The recognition of 
subgenera within the large and widely under¬ 
stood genus Neochonetes was discussed by Arch¬ 
bold (1981). 
Neochonetes hockingi sp. nov. 
Fig. 2A-R 
Etymology. Named for geologist Roger M. Hocking, 
discoverer of the chonetid band which yielded the 
species. 
Holotype. GSWA FI 1 247, a natural ferruginous cast of 
a ventral valve exterior showing the external orna¬ 
ment, from GSWA locality 94217, Billidee Formation, 
collected by Dr S. K. Skwarko, Geological Survey of 
Western Australia. 
Paratypes. GSWA F43818-F43820, two natural casts 
of dorsal valve exteriors and one external mould of a 
dorsal valve; GSWA F43821, F43822, two natural 
casts of shells; GSWA F43823-F43826, four natural 
casts of ventral valve interiors; GSWA F43827, 
F43828, two natural casts of ventral valve exteriors; 
and GSWA F43829-F43834, live natural casts ofdor¬ 
sal valve interiors and one natural internal mould of a 
Fig. 2. Neochonetes (Sommeriella) hockingi sp. nov. A, GSWA F43818, natural cast of dorsal valve exterior, x 
3.5. B, GSWA F43819, latex cast of dorsal valve exterior, x 3.5. C, GSWA F43820, natural cast of dorsal valve 
exterior, x 3.5. D, GSWA F43821, natural cast of shell in dorsal view, x 3.5. E, GSWA F43823, natural cast of 
ventral valve interior, x 3.5. F, GSWA F43822, natural cast of shell in dorsal view, x 3.5. G, GSWAF43824. 
natural cast of ventral valve interior, x 3.5. H, GSWA F43825, natural cast ventral valve interior, x 3.5.1. GSWA 
F43826, natural cast of ventral valve interior, x 3.5. J, GSWA FI 1247, holotype, natural cast of ventral valve 
exterior, x 3.5. K, GSWA F43827, natural cast of ventral valve exterior, x 3.5. L, GSWA F43828, natural cast of 
worn ventral valve exterior, x 3.5. M, GSWA F43829, natural cast of dorsal valve interior, x 3.5. N,G$WA 
F43830, natural cast of juvenile dorsal valve interior, x 3.5. O, GSWA F43831, natural cast of juvenile dorsal 
valve interior, x 3.5. P, GSWA F43832, latex cast of dorsal valve internal mould, x 3.5. Q, GSWA F43S33, 
natural cast of dorsal valve interior, x 3.5. R, GSWA F43834, natural cast of dorsal valve interior, x 3.5. 
