Taxon description
Bromley & Hanken, 1991
Diagnosis: Unwalled, vertical or subvertical shafts, thediameter increasing upward, giving offside branches hav-ing a morphology and orientation similar to that of themain shaft.
Classification
Diagnosis: Unwalled, vertical or subvertical shafts, thediameter increasing upward, giving offside branches hav-ing a morphology and orientation similar to that of themain shaft.