David J. McCutchion says that the lower structure of the pinnacled or ratna design is a rectangular box with a curved cornice.

The simplest form has a single central tower (eka-ratna), to which may be added four more at the corners (pancha-ratna)”.

By increasing the towers or pinnacles to nine (nava-ratna), thirteen, seventeen and twentyone up to a maximum of twentyfive.

McCutchion classifies the Shantinatha Shiva temple as a West Bengal nava-ratna with ridged turrets.

[1] The Shantinath Shiva temple, with nine pinnacles, has exquisite terracotta which showcases the Ramayana battles, several scenes from Krishna lila, Bhisma on a bed of arrows, Dasavtar of Vishnu, several musicians etc.