The figure below shows the distribution of samples containing the brachiopod Sowerbyella.

Sowerbyella distribution

Sowerbyella is a common strophomenid brachiopod in the MRV strata.

[ Sowerbyella ]

Sowerbyella Jones, 1928 [*Leptaena sericea Sowerby, 1839]
Parvicostellae either smooth or slightly beaded and variably segregated; ventral muscle scar small and bilobed, bounded posterolaterally by short dental plates and anteromedianly by pair of divergent ridges bifurcating from short median ridge bearing adductor scars; brachial valve with pair of strong submedian septa flanked by raised suboval areas, median ridge variably developed.
Ord. - L. Sil., cosmopolitan
Family Sowerbyellidae Opik, 1930
Semicircular to semioval, unequally parvicostallate, with small pseudodeltidium, apical foramen rarely if ever persistent in adult shells. Small teeth rarely supported by dental plates and rarely supplemented by denticles; variably bilobed ventral muscle scar with deeply inserted lanceolate adductor scars; chilidial plates fused with small flat-lying socket ridges and median ridge-like cardinal process to form inverted V which overhangs subcircular deep depression in place of notothyrial platform; dorsal septa and lophophore platform variably developed; ventral and dorsal mantle canal patterns digitate to lemniscate.
Ord. - M. Dev.
Order Strophomenida Opik, 1934

Treatise on Invertebrate Paleontology, H378-379