Central sclerite complex of B. transversale subgroup A, B B. transversale (vouchers V101437 and V101436, USA: Michigan: Port aux Pins, Bois Blanc Isl.) C, D B. erosum (vouchers V101440 and V101439, USA: California: Del Norte Co., Wilson Creek, 3 m, 41.6051°N, 124.1005°W) E, F B. corgenoma (vouchers V101428 and V101430, USA: Oregon: Benton Co., Corvallis, Willamette River, 44.5475°N, 123.2428°W). Scale bar: 0.1 mm.