At the middle, or in the distal half, each spine bears a verticil of three strong, irregularly formed ramified branches.
verticil: one of the whorls of long fine sensitive hair arranged symmetrically on the joints of the antennae in certain Diptera.
Each spine between the two shells has a verticil of three forked lateral branches (fig. 9a).
The distal end of each radial tube bears usually a verticil of four to eight similar pediculate spathill.