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.