. Bulletin of the British Museum (Natural History), Geology. . Fig. 9 Myofossa (Myofossa) subarbitrata (Dickins). Lower Permian, Nura Nura Member of Poole Sandstone Formation, 1-6 miles SW of Paradise Homestead, Canning Basin, Western Australia. Figs 9a-c, BMR CPC 3885, holotype; Fig. 9a, top view; Fig. 9b, oblique view showing siphonal area; Fig. 9c, view of left side; all x3. Figs 9d-e, BMR CPC 3886, paratype A; Fig. 9d, view of left valve; Fig. 9e, top view; both x2. Fig. 9f, BMR CPC 3887, paratype B, side view showing slight subumbonal sulcus, x3. significant gape. A narrow ligament groove
. Bulletin of the British Museum (Natural History), Geology. . Fig. 9 Myofossa (Myofossa) subarbitrata (Dickins). Lower Permian, Nura Nura Member of Poole Sandstone Formation, 1-6 miles SW of Paradise Homestead, Canning Basin, Western Australia. Figs 9a-c, BMR CPC 3885, holotype; Fig. 9a, top view; Fig. 9b, oblique view showing siphonal area; Fig. 9c, view of left side; all x3. Figs 9d-e, BMR CPC 3886, paratype A; Fig. 9d, view of left valve; Fig. 9e, top view; both x2. Fig. 9f, BMR CPC 3887, paratype B, side view showing slight subumbonal sulcus, x3. significant gape. A narrow ligament groove is shown behind pe umbo in BM L47314 and the hinge appears to be 3dentulous. The ribbing is distinctive. In the holotype, 16 ribs can be counted in the front part of the shell which are more or less concentric. The rib number increases rapidly by inter- polation and 39 are present in the most tumid part of the shell; some of the added ribs make a distinct Y-like bifurca- tion with ribs at the front. A rounded posterior adductor muscle scar is shown in BM L3231 and the back part of the oallial line has a shallow sinus. BM L47515, from Redesdale, has a well-preserved short lymph with a narrow, lunate ligament groove separating it Tom the escutcheon. Its inner surface is juxtaposed to the Jther nymph and does not project inwards from the remain- ng part of the posterior dorsal shell margin. Remarks. Hind (1900: 381) recognized that M'Coy (1851a: |74; 1855: 508; pi. 3f, figs 6, 6a, 7, 7a) had included two listinct shells in Sanguinolites variabilis. Elsewhere (p. 69) we lave pointed out that the specimen in M'Coy, 1855: pi. 3f, fig. 5, 6a, is the lectotype of Cosmomya variabilis (M'Coy), .elected by Hind (1900), and a new name is now required for he other specimen. Driscoll (1965: 91) included this species is a synonym of Myofossa [Grammysia] omaliana (de Koninck) n his redescription of that species. However, although Myo- fossa hindi has a similar shape to M. omaliana, the orname
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