. Bulletins of American paleontology. 16 Bulletin 185 has now altered somewhat. The hirge number of polygonal plates, rather irrecular in size, form and arrangement, few of which can be homolomzed even from individual to individual, point to an archaic plan of which the amphorideans may well be the archetype. The thecae of the earliest Soluta are the most inflated, thus most closely approaching the vasiform of the amphorideans. Likewise the earliest dendrocystitid heterostele is most reminiscent of the amphoridean attenuate, but polyplacate, peduncle. In both, the thecal plates commonly show a
. Bulletins of American paleontology. 16 Bulletin 185 has now altered somewhat. The hirge number of polygonal plates, rather irrecular in size, form and arrangement, few of which can be homolomzed even from individual to individual, point to an archaic plan of which the amphorideans may well be the archetype. The thecae of the earliest Soluta are the most inflated, thus most closely approaching the vasiform of the amphorideans. Likewise the earliest dendrocystitid heterostele is most reminiscent of the amphoridean attenuate, but polyplacate, peduncle. In both, the thecal plates commonly show a tendency to develop central bosses which culminate in the spinose processes of Rntroclypens. The outline of the flattened theca of the Soluta varies from the pyriform quadrilateral of early forms, through cordiform, tetralobate to subcircular in the terminal forms (see text-figure 2). Family DENDKOCYSTITIDAE Bassler, 193S D/agiws/s.—Sol//fa hav/ng thecae of no defin/te geo/r/etrical jorm; n/onohrach'/al: iv'/th a tendency to develop additional nons/ibvective thecal extensions: theca composed entirely of polygonal plates: an//s at proxin/al end near stele. Theca and stele son/ewhat inflated. Proxin/al and distal parts of stele well differentiated. Genus Heckericystis Gill and Caster, new genus Diagnosis of gen/is.—Dendrocystitids with proximal stele consisting of terete ann//li of f/ised plates. Type species.—Heckericystis k//ckersiana (Hecker). Baltic Text-fig. 3.—Heckericystis kuckersiana (Hecker) from tlie Baltic Ordovician. From Hecker, 1940. Comment.—Hecker (1940) said of this species: Along the longitudinal axis, the theca has the form of a more or less equilateral triangle ... By all appearances, the shape of the theca in live specimens of D. kuckersiana was not circular but flattened in section . . Plates comprising the theca are placed in a mosaic-like fashion; they are of irregular polygonal shapes usually pentagonal, though not more than heptag
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