[2] Those two species split 3.10 million years ago (Isthmus of Panama formed 3.1–3.4 Mya).

Pease' original text (the type description) reads as follow: Oval, rather rugose, convex above.

Tentacles arising from the head, curving laterally, deeply grooved below, truncated, cylindrically tapering, transversely lamellated.

Colour varying; some bright red, others lemon-yellow, or purplish brown, others again variegated with whitish; beneath paler than above.

Shell on the anterior half of the body, concealed, small, fragile, pellucid, oblong-ovate, convex, and ornamented with wrinkles of