Dart Screw Shell, Turritella radula

Dart Screw Shell, Turritella radula. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, March 2015. Size: 8.2 cm (3.2 inches) x 1.7 cm (0.7 inches).

The Dart Screw, Turritella radula (Keiner, 1843), is a gastropod mollusk that is a member of the Turretellidae Family of Turrets. The shell has sixteen to twenty deeply convex whorls that have two beaded ridges that follow along the whorls and finely beaded lines in between these ridges. The exterior of the shell is marbled with yellowish-brown, and darker brown and white; the interior is brown or white with brown blotches. The Dart Screw Shells reach a maximum of 10.0 cm (3.9 inches) in length and 2.1 cm (0.8 inches) in height..

 Dart Screws are found over and within sand substrate at depths between 10 m (35 feet) and 150 m (500 feet). They range from Cedros Island, Baja California to Ecuador, including the Galapagos Islands. They are found in the Sea of Cortez from La Paz to the greater Cabo San Lucas area, Baja California Sur.

A synonym is Turritella mariana.