Criocone

Small planospiral criocones with partially coiled whorls (microconchs) or completely uncoiled (macroconchs). Whorl-section hexagonal, rounded up to round. The protoconch and the first whorl unknown, but [...]

[...] disturbance to such a form might produce rapid acceleration in two ways — in shape, from serpenticone to criocone, in ornament, from tuberculate to costate, that is, costate post-tuberculate.