> Orbitolites (figs. 5, 6) we have a centre on a somewhat Milioline type; and after a few chambers in spiral succession, complete circles of chambers are formed. In the larger forms the new zones are of greater height, and horizontal bulkheads divide the
chamberlets into vertical tiers, each with its own pylomic pore.
[Illustration: FIG. 4.--Modifications of Peneroplis. 1, Dendritina; 2, Eu-Peneroplis.]
[Illustration: FIG. 5.--Shell of simple type of Orbitolites, showing primordial chamber a, and circumambient chamber b, surrounded by successive rings of chamberlets connected by circular galleries which open at the margin by pores.]
[Illustration: FIG. 6.--Animal of simple type of Orbitolites, showing primordial segment a, and circumambient segment b, surrounded by annuli of sub-segments connected by radial and circular stolon-processes.]
The Cheilostomellidae (fig. 3, 13) reproduce