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- C6 Sequence (Upper Whitewater, Elkhorn)
Identification in Hand Sample
- Five ambulacra
- Five diamond-shaped pore rhombs
- Column about three times as long as the theca
- Weak ridges on thecal plates
Lepadocystis moorei from the Elkhorn Formation of Preble County, Ohio (MUGM T-), stem from the Waynesville Formation of Waynesville, Ohio (OUIP 1445), far right specimen from Eaton, Ohio (CMC 59164).
Holland (UGA Strat Lab, 2013):
- Weak ridges on thecal plates, long ambulacra, and five diamond-shaped pore rhombs.
- Shape. – Very young theca (Pl. III, Fig. 1) ovoid, globose. Immature thecae (Pl. II, Figs. 1-4; Pl. III, Fig. 2; Pl. IV, Figs. 1-6) semiellipsoidal, slightly compressed along axis of radius III-interradius 5. Mature specimens (Pl. VI, Fig. 6) of about the same shape as immature, a little more compressed. Very large theca (presumably gerontic) (Pl. VI, Fig. 8) subpyriform, aborally tapering to the junction with the stem and very broad through the upper part of the LL circlet.
- Thecal plates. – Four basals, as usual in callocystitids, forming a closed circlet, with B1, B2, and B3 pentagonal and B4 hexagonal. B2 with aboral half of pore rhomb. Aboral edge of basals bearing a circular groove for juncture with the stem (Pl. I, Fig. 5; Pl. III, Fig. 2; Pl. IV, Fig. 10). In a few, however, L3/L4 junction expressed as a short, sloping suture, more or less a continuation of the L3/R3 suture (Pl. II, Fig. 1; Pl. IV, Fig. 4). L1 and L2 hexagonal, their aboral angles inserted between IL1 and IL5 and between IL1 and IL2 respectively; L3 and L4 pentagonals, in which case they meet at a point and their sides together form an X, or subhexagonal, in which case they meet along a short suture; L5 subtrapezoidal, with sides converging orally and aboral side distinctly and deeply indented around periproct (Pl. I, Fig. 3; Pl. II, Fig. 2; Pl. IV, Fig. 3). Half-rhombs on all LL except L5.
-Radials five, the circlet interrupted by L5 between R4 and R5 (Fig. 1b), not complete. R1 and R2 irregularly subhexagonal; R3 subpentagonal, nearly square but with a truncated oral corner (Pl. I, Fig. 5; Pl. IV, Fig. 4); R4 the smallest of the RR, subpentagonal, bounded by L4, L5, R3, O4, and O5 (Fig. 1b); and R5 somewhat subtrapezoidal, with its longest side in contact with L1. R1 and R5 with half-rhombs, and R3 with two half-rhombs.
-Orals five, small and partly obscured by ambulacra, surrounded by all RR and L5. Exposed part of O1 panduriform, sides of plate covered by flooring plates of ambulacra I and V; exposed parts of other OO consisting of semicircular areas adjacent to the peristomial region and aboral entensions between the lobate initial flooring plates of the bordering ambulacra, each thus shaped like the head of medieval battle-ax. Each oral bordering on the long, narrow peristome, insofar as we can infer from the exposed parts, with all OO five-sided except O5 which is six-sided (Fig. 1b). Each oral in contact with two RR, and O5 also in contact with L5 along its aboral edge. O1 the largest oral, tripartite with a small sector bordering the peristome and O5, a larger sector aboral to it, and a very large, nearly semicircular one at the left (Pl. II, Figs. 9-10; Pl. IV, Fig. 1). Suture between the two larger sectors passing through the centers of hydropore and gonopore.
-Plate arrangement in UMMP 5426a (Pl. I, Figs. 1-6; Pl. II, Figs. 5-10) abnormal. IL1 represented by two plates, the aboral right (IL1a) pentagonal and the oral left (IL1b) quadrate (Fig. 1a). The two plates occupying more area of the theca than IL1 in normal specimens (compare Pl. I, Fig. 4 with Pl. VI, Fig. 6). L1 a little larger than normal and septagonal instead of hexagonal, the extra angle fitting between IL1a and IL1b (compare Pl. II, Fig. 7 with Pl. II, Fig. 3).
-Inner surface of thecal plates marked by growth lines (Pl. V, Fig. 1), revealing growth of each plate (including rhomb areas) to be holoperipheral.
-Ornamentation variable at each growth stage. Plate of very small theca (Pl. III, Fig. 1) marked by conspicuous ridges between centers of BB, ILL, LL, and RR and a few low tuberculate elements; ridges primarily perpendicular to sides of the plates, with no discernible radial elements leading to the corners. In slightly larger juvenile specimens, radial elements leading to the corners. In slightly larger juvenile specimens, radial elements leading to the corners, as rows of partly fused tubercles (Pl. III, Fig. 2, at the left; Pl. VI, Fig. 10) or as nearly complete ridges (Pl. III, Fig. 2 at the center; Pl. IV, Figs. 3-5, Pl. VI, Fig. 7). In addition to the radial elements at this stage, other elements nearly perpendicular to the edges of the plates, either as rows of tubercles (Pl. III, Fig. 2; Pl. VI, Fig. 7) or as ridges (Pl. IV, Fig. 5), and some irregularly places low tubercles. In adult and gerontic specimens, ridges and tubercles becoming faint (Pl. I, Figs. 3-6; Pl. VI, Fig. 6) or very low and almost indistinct (Pl. VI, Fig. 8).
-A scoop-like depression on L5, extending orad and slightly to the left from the periproct, enclosed by a faint ridge (Pl. I, Fig. 6; Pl. III, Fig. 2, at the right).
- Ambulacra. – Five ambulacra.
- Pore rhombs. – Five rhombs.
- Peristome. – Peristome a long narrow slot with one branch extending from the oral end to ambulacrum III to the junction of I and II at the left and another branch from III to the junction of IV and V at the right. Right branch longer than left.
- Periproct. – Periproct enclosed by IL4, IL5, L4, and L5. Scoop-like depression extending from periproct orad and slightly to the left on L5, as noted above. Plates of periproct consisting of a central pyramid of six plates and an outer ring of numerous small subquadrate plates.
- Hydropore and gonopore. – Hydropore and gonopore present in all specimens, young (Pl. IV, Fig. I), adult (PI. 11, Figs. 9-10), and old (PI. VI, Fig. 9), each bisected by a suture within 01 (Fig. la).
- Column. – Column in some specimens joined to theca along a plane normal to the thecal axis, but in others joined along a sloping plane that extends farther aborally in interradius 1 than in interradius 5 (PI. I, Figs. 4-5 ; P1.11, Fig. 3), causing the column to slope away from the theca toward the side opposite the periproct. Column only about three times as long as the theca.
- The following is an attempt at an independent analysis of the plate system of the type, which is intended to show where the details are clearly defined and where they are imperfectly exhibited by the type specimen. This diagram differs but slightly from that presented by Bather in his volume of the Echinoderma, forming Part III of Lancaster’s Treastise on Zoology, published in 1900.
- In this diagram, the character if the surface ornamentation, consisting chiefly of parallel lines radiating in different directions, is indicated, wherever preserved. The ornamentation of plate 13, and of plates 15 to 19, probably was very faint or practically absent. The outlines of plates 11 and 17, and those of the adjacent parts of plates 5, 6, and 12 are so poorly defined that they can not be indicated with exactness. The surface ornamentation of plates 11-17 was detected only after their presence had been discovered on other specimens on which the surface of these plates was well preserved. A small fragment, probably belonging to plate 13, is drawn in this analysis as though a part of plate 14. This is the fragment drawn by Meek, in his diagram of this specimen, printed on one of the pages interleaved between the index and the numbered plates, at the close of vol. i, of the Paleontology of Ohio, in 1873, as though it were a fifth plate in contact with the anal area.
- The anal area is composed of two circles of plates, of which the type preserves only three plates belonging to the lower part of the outer circle. The two plates in contact with plate 7 are pentagonal and bear a central tubercle, as described by Meek. A third plate, of a similar character, is in contact with plate 14. Judging from other specimens, the co-called central tubercle, on each of the three lower plates of the anal area may be regarded merely as a continuation of the parallel line ornamentation belonging to the top of plates 7 and 8. From other specimens it is known that the plates forming the top and upper left-hand sides of the outer circlet of plates, in the anal area, are of much smaller size than the lower plates, thus reducing the width of the upper part of the outer circlet. The two plates indicated in the upper part of the anal circle therefore are incorrect, and should be replaced by a row of much smaller plates.
- The ambulacral arms are clearly outlined. Those parts of the thecal plates upon which they rest are flattened, but not indented or depressed. The arms or ambulacra are longer, more linear, and narrower at their proximal extremities than indicated by Meek’s Figure, 4c. Ambulacral plates with facets for attachment of the brachioles at alternate sutures of the ambulacral plates. At these areas of attachment the two adjacent plates form a single rounded low knob, projecting beyond the lateral contour of that part of the plates which intervenes between the points of attachment for the brachioles. The side of each knob is impressed by a single facet. Ambulacralia present but not clearly defined.