11. The shell is gibbous adorally, such that the body chamber is widest well behind the aperture. 12. It begins as a barrel shaped cadicone, with an eccentric, more or less smooth body chamber . 13. Secondary ribs become thicker on the body chambers of microconchs but thinner of body chambers of macroconchs. 14. Shells enlarge moderately to the middle of the mature body chamber , then contract gently toward the aperture. 15. Secondary ribs become thicker on the body chambers of microconchs but thinner of body chambers of macroconchs. 16. They have developed shorter body chambers than in the ancestral Arietitidae, resulting in more stable floating positions. 17. The venter, especially of the chambered phragmocone is convex in profile; the body chamber long and tubular. 18. Large forms have simple apertures and smooth body chambers while small forms have lappets and ribbed body chambers. 19. Large forms have simple apertures and smooth body chambers while small forms have lappets and ribbed body chambers . 20. The adult body chamber may equal or exceed the length of the chambered part of the orthoconic section.
