_Genus_--TETRACLITA.
Fig. 1 _a_, Tetraclita porosa, _var._ communis.
1 _b_, " " " rubescens.
1 _c_, " " " nigrescens.
1 _d_, " " " elegans.
1 _e_, " " " communis, young, with radii
developed.
1 _f_, " " " patellaris.
1 _g_, " " basal edge of wall of shell.
1 _h_, " " basal edge of wall of shell, _var._
elegans, showing also the
structure of one of the
rudimentary radii or sutures.
1 _i_, " " internal view of scutum; 1 _k_, do.
of tergum; 1 _l_, do. of scutum,
_var._; 1 _m_, do. of tergum, _var._
2 _a_, Tetraclita serrata; 2 _b_, portion of external surface
of wall, low down, near basis; 2 _c_ and 2 _d_, scutum and
tergum, internal views.
3 _a_, Tetraclita rosea, scutum; 3 _b_, tergum; 3 _c_, whole
shell; 3 _d_, basal edge of wall of shell.