This is a very new form. The Pleiades form was invented in 1999 by Craig Tigerman, Sol Magazine's Lead Editor. The Pleiades is a star cluster in the Taurus constellation discovered by the Greeks and named the Seven Sisters, Alcyone, Asterope, Celaeno, Electra, Maia, Merope, and Tygeta.
The basic form consists of seven lines, each line starting with the same letter as the title, and at first no meter or syllable count was specified. Here is an example of that basic form.