Brightest members of the Pleiades (plus the B8 V primary standard 18 Tau, also a member), ordered (from top to bottom) by brightness. 27 Tau (Atlas), 19 Tau and 18 Tau are the primary standards for their respective types, while 20 Tau is a useful standard for B7 III, because of its narrow lines, η Tau (Alcyone) was the original primary standard for B7 III, but was discontinued because of its shell episodes. In addition, it appears too luminous to be representative of the type. A fainter shell star, 28 Tau (Pleione = HD 23682) was not observed.