Preferred orientation of Turritella

Fossil shells belonging to the shallow-marine gastropod Turritella are prone to have been preferentially aligned by waves and currents because their shells are long an straight. I used the first slide below in one of my earlier posts (July 24, 2014) on the subject of "Taphonomy of Mollusks Shells." Taphonomy is the study of post-mortem processes (waves, currents, bored by other organisms, etc.) that affect shells.

Eocene Turritella andersoni lawsoni shells in the Llajas Formation
of Simi Valley, Ventura County, Southern California. The
longest shell is 6 cm long. These shells occur in situ, in
a bed of silty fine-grained sandstone.

More Eocene T. andersoni lawsoni shells from the Llajas Formation
of Simi Valley. The longest shell is 6 cm long. This slab is a piece of
loose rock ("float") from the formation.