PLATE VI. 
Figs. 1, 2, 8, 22, Attenuate forms. 
Figs, 35.49 53103) ge, 23), Veutricose forms. 
Fig. 9, Spires from which the jugum has been broken. 
Figs. 10, 11, Two casts of the interior of the ventral valve. 
Figs. 1, 3, 4, 21, 22, Show a marked fasciculation of striz. 
Figs. 19, 20, Exfoliated specimens. 
Figs. 4, 8, 12, More general forms. 
Figs. 15-31, Young specimens. 
