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Zoopiiyta] LOWER PALAEOZOIC RADIATA. 33 Genus. Clisiopiiyllum {Dana). Etym.—KXi'o-iov, a tent (from the conical central boss). Gen. Char.—Corallum simple, branched, or aggregate, with vertical radiating lamellse; a thin epitheca or outer wall: internal structure (vertical section), central area composed of small vesicular plates and cells converging or arching upwards to the centre, so as to form a conical boss in the cup; no distinct central axis; outer area of small cellular structure, inclining in the opposite direction or upwards and outwards, separation between these areae formed by an intermediate area of larger, nearly horizontal, cellular structure; (horizontal section) a large central area of small irregular cellular texture, from which the primary lamella' radiate to the outer walls, intermediate zone with few vesicular plates between the lamellse; outer zone having the primary and secondary lamellse connected by very numerous vesicular plates. The upward wave of the vesicular plates in the middle area of the vertical section, and consequent projecting boss in the middle of the cup, separate this genus from some of the radiated Cystipliylla. Clisiophyllum vortex (M c Coy). PI. 1. B. fig. 18. Ref— M c Coy, Ann. Nat. Hist. 2nd Series, Yol. VI. p. 277. S 1 <p. Ch.—Corallum simple, conic, slightly curved, enlarging at the rate of one inch eight lines in three inches from the apex; outer wall thin, faintly marked with subequal longitudinal lamellar strise (five or six in the space of three lines at a diameter of one inch), and small concentric wrinkles; at a diameter of one inch the horizontal section shews an outer area of about sixty thick, equal, radiating lamellse, barely reaching one-fourth of the diameter towards the centre, connected by small irregular transverse vesicular plates; a few of the pairs have a very thin, short, marginal lamella between each of the larger pairs, and where this occurs the vesicular transverse plates become much more numerous; inner area rather more than half the diameter, forming a circular mass of confused vesicular tissue, crossed by a few arched radiating delicate lamellse: vertical section, having the narrow outer area on each side (corresponding to the lamelliferous zone) of arched vesicular plates, forming large unequal horizontal or slightly inclined cells, one or two cells extending across the width of the area; wide inner area composed of small oval cells arranged in much-curved transverse rows, the convexity of the curve upwards. Position and Locality.—Wenlock limestone, Wenlock, Shropshire. Explanation of Figures.—Plate 1. 15. fig. 18. Natural size from Wenlock.—Fig. 18 a. Do. Vertical and horizontal sections near base, natural size, shewing the very large vesicular inner area of rows of upward-curved cells, the narrow outer area containing the primary radiating lamellse in the horizontal section, and large vesicular tissue in the vertical section; and the extremely narrow layer of minute vesicular tissue lining the wall and corresponding to the short secondary lamellse in the horizontal section. 3rd Subfamily. NEMATOPIIYLLINiE. Corallum rarely simple and turbinate, usually compound, of numerous polygonal tubes; in either case each cell defined, by a distinct, solid, outer wall or epitheca, within which is a vesicular outer or perithecal area, either radiated or not, by the costal extensions of the lamellse; wdthin this outer zone is an inner cylindrical area, forming the true cell-tube, defined by a thin wall and containing the radiating lamella', of two sizes, connected by numerous transverse vesicular plates ; usually a distinct central axis. The corals of this subfamily are distinguished by the perithecal zone round the cell-tubes, defined for each individual by a solid boundary wall or epitheca, sometimes single, sometimes double in the massive species. Genera:—1, Nemaiophyllum; 2, Stylaxis; 3, Stromlodes; 4, Lonsdaleia; 5, Stylastrcea; 6, Acervularia ; 7, Siphonodendron.