Original Description of Helicaulax costata by Gabb, 1869, p. 167:
- "SHELL small, broadly fusiform, spire elevated ; whorls six or seven, angulated in the middle, sloping, and nearly straight above, slightly convex below; above the angle are numerous fine striae, below are five or six subacute revolving ribs, with broad concave interspaces. Aperture broad above, narrowed in front, posterior canal well marked, and curving backwards; outer lip and anterior canal unknown ; inner lip thinly incrusted."
Locus typicus: Martinez, Contra Costa County, California, USA
Stratum typicum: Martinez Formation, Eocene
Types: Academy fo Natural Sciences of Philadelphia no. 4281: Holotype
Helicaulax costata Gabb, 1869, pl. 28, fig.48
- Gabb, 1869. Calif. Geol. Surv. Paleont. vol. 2, p. 167, pl. 28, fig. 48