_Genera_--TETRACLITA AND ELMINIUS.
Fig. 1 _a_, Tetraclita purpurascens, _var._ with surface
disintegrated, and with the sutures united and obliterated.
1 _b_, Tetraclita purpurascens, _var._ well preserved, with
the radii developed; 1 _c_ and 1 _d_, _var._ scutum and
tergum, internal views.
2 _a_, Tetraclita costata; 2 _b_ and 2 _c_, scutum and tergum.
3 _a_, Tetraclita vitiata; 3 _b_, basal edge of portion of
wall; 3 _c_ and 3 _d_, scutum and tergum, internal views
of; 3 _e_, tergum, internal view, _var._
4 _a_, Tetraclita cœrulescens; 4 _b_, scutum and tergum
united, external view; 4 _c_ and 4 _d_, scutum and tergum,
internal views.
5 _a_, Tetraclita radiata; 5 _b_, scutum and tergum united,
external view; 5 _c_ and 5 _d_, scutum and tergum, internal
views.
6 _a_, Elminius Kingii; 6 _b_ and 6 _c_, scutum and tergum,
internal views of; 6 _d_, tergum, _var._ external view of;
6 _e_, tergum, another _var._ internal view of.