PLATE XIIa.*
                          GOMPHOCYSTJTES TENAX, HALL.
                                         Page 352.
FIG. 1. Lateral view of the upper part of the body, showing the arrangement
of plates; the
             spiral grooves indicating the places of the sessile arms are
at the upper margins of the
             ranges of smaller plates. The plates are more or less irregularly
disposed in some
             parts of the body, but they appear, like others of the genus,
to have a generally
             spiral arrangement. (Enlarged to two diameters.)
      2. The summit, showing the arrangement of the spiral arms and the central
aperture. The
             diagram is made from an imperfect specimen, and the position
of the eccentric
             aperture could not be ascertained.
                          GOMPHOCYSTITES CLAvUS, HALL.
                                         Page 353.
FIG. 3. A fragment (natural size), showing the disposition of the spiral
arms and the obtusely
             angular form of the body below.
                          GomPHOCYSTIrES GLANS, HALL.
                                         Page 352.
FIG. 4. Lateral view of a specimen, showing the entire form and the disposition
of the spiral
             arms.
 I   5. The anterior ? view of another individual of the same species.
                        HOIOCYSTITES ALTERNATUS, HALL.
                                         Page 865.
FIG. 6. A posterior ? view of a specimen (natural size), showing the position
of the eccentric
            aperture, form and relation of plates, etc.
                        HOLOCYSTITES CYLINDRICuS, HALL.
                                         Page 854.
FIG. 7. View of a nearly entire individual, showing the central aperture
in a depression at the
            summit. The plates of the lower part are broken off.
 "   8. A smaller individual, in which the plates have been strongly
ridged, preserving a portion
            of the column. The lower ranges of plates are somewhat obscure,
and the dotted
            lines indicate depressions, which may be sutures or only grooves
in the larger plates.
                            APIOcySTITES IMA GO, HALL.
                                         Page 358.
FIG. 9. Lateral view of the specimen, showing the ovarian aperture on the
left-hand side of the
            figure, and the right pectinated rhomb. (Figure natural size.)
                         CRIAOCYSTITES CHRYSALis, HALL.
                                         Page 362.
FIG. 10. View of the gibbous side of the specimen.
" 11. Lateral view of the same specimen.
*This plate accompanied the original paper as Plate I. It is now arranged
with the other plates in its order
as XII4.