TABLE 4. Summary of characters and character states for cladistic analysis.

				States
		Character	0	1	2
	1	Pegma or pegma-like structure	Absent	Present
	2	Development of pegma	Weak	Moderate	Strong
	3	Divided shell	Absent	Present
	4	Degree of coiling	Up to 1 coil	1 or more coils
	5	Raised sub-apical aperture lip	Absent	Raised lip or siphon
	6	Internal shell ridges	Absent or faint	Present
	7	Curved ventral margin	Absent	Present
	8	Univalved or bivalved larval shell	Univalved	Bivalved
	9	Lateral compression	Absent	Present
	10	Ratio of length:height	Less than 1.5	1.5 or more
	11	Prismatic shell layer	Absent	Present
	12	Inner laminar layer	Absent	Present
	13	Inner calcite layer	Absent	Present
	14	Shell pores	Absent	Present
	15	Spiny layer (lamello-fibrillar)	Absent	Present
	16	Stepwise inner layer	Absent	Present
	17	Calcitic semi-nacre	Absent	Present
	18	Prismatic best preserved near apex	Absent	Present
	19	Coiling loss; straight dorsal margin	Absent	Present
	20	Aperture constriction	Absent	Pinched near sub-apical margin
	21	Aperture shape	Sub-apical width greatest	Supra-apical width greatest