21.   The first ventral arm plate is pentagonal with the lateral edges raised forming a boundary lip to the second oral tentacle pores.

22.   The plate itself is a small rectangle of metallic material.

23.   The plates are quite rare.

24.   The tectonic plates are no more permanent than the sovereign countries of the world.

25.   The ventral arm plates are an irregular pentagonal or hexagonal shape, often keeled, with the distal edge sometimes indented.

26.   The ventral arm plates are nearly pentagonal with a distinct convex distal edge textured with layers of calcite forming a concentric pattern.

27.   The ventral arm plates are not contiguous.

28.   The ventral arm plates are pentagonal often with a rounded distal edge, and are separated.

29.   The ventral arm plates are pentagonal with a wide distal edge, and contiguous on proximal arm segments.

30.   The ventral arm plates are pentagonal with an acute proximal angle, a slightly indented distal edge, and separated from one another.