Osgoodicystis Frest & Strimple, 2011

Fig. 12. Photographs of oral areas in holocystitid blastozoans,showing the mouth (M) and anus (An) and the five ambulacral facets (A–E), Massie Formation, Sheinwoodian, Napoleon, Indiana, USA. A. Osgoodicystis bissetti Frest & Strimple in Frest et al., 2011, SUI 48166; black arrow points to the suture between the A ambulacrum facetal and the orals, white arrows point to the oral ends of the A and C food grooves, respectively, both of which follow sutures between orals. B. Pentacystis gibsoni Frest & Strimple in Frest et al., 2011, SUI 46316; white arrows point to the oral ends of the A and B food grooves, respectively, both of which lie entirely on their respective facetals. C. Moyacystis cooperi (Frest & Strimple in Frest et al., 2011), SUI 48167; arrows point to food grooves of the D and E ambulacra.The E food groove crosses the entire peristome margin on a facetal plate.A and B from Sheffield and Sumrall (2017: fig. 6.5 and 6.3, respectively); C from Frest et al. (2011: pl. 14: 1).

Fig. 13. Oral plating in holocystitid blastozoan Osgoodicystis bissetti Frest & Strimple in Frest et al., 2011, SUI 48166, Massie Formation, Sheinwoodian lower Silurian), Napoleon, Indiana, USA.A1, original photograph of holotype (from Frest et al. 2011: pl. 12: 1); A2, photograph with outlines of plates, facets and food grooves superimposed;A3, interpretive diagram, not to scale.Abbreviations:A–E, Carpenter’s (1884, 1891) ambulacral designations;An, anus; M, mouth.

Fig. 14. Facet of ambulacrum C in holocystitid blastozoan Osgoodicystis bissetti Frest & Strimple in Frest et al., 2011, SUI 48166, Massie Formation, Sheinwoodian (lower Silurian), Napoleon, Indiana, USA.A1, original photograph (from Frest et al. 2011: pl. 4: 5); A2, photograph with outlines of plates, facet and food grooves superimposed; A3, interpretive diagram. Abbreviations: C, Carpenter’s (1884, 1891) ambulacral designation; FG, food groove from facet to mouth (M); O5 and O6, oral plates 5 and 6; rings in O6 within peristome, oral pores; PO, perioral plates. Note that the food groove follows the suture between the orals.

Fig. 1. Interpretive diagrams of oral plating in some holocystitid genera. A. Holocystites Hall, 1864, with six oral plates forming the mouth frame, eight facetal plates and five ambulacral facets shared between plates of both circlets (1–8, facetals). Based on USNM S3070, Holocystites cylindricus (Hall, 1861), from Paul (1971: fig. 26c). B. Pentacystis Paul, 1971, with no orals, eight facetals and five facets. Based on AMNH 20271a, Pentacystis simplex Paul, 1971, from Paul (1971: fig. 42b). C. Trematocystis Jaekel, 1899, with six orals, eight facetals and four facets. Based on UMMP 45862, Trematocystis globosus (Miller, 1878), from Paul (1971: fig. 50a). D. Pustulocystis Paul, 1971, with six orals and facetals plus four facets (1–6, orals). Based on AMNH 20273, Pustulocystis ornatissimus (Miller, 1891), from Paul (1971: fig. 58a).Abbreviations:A–E, Carpenter’s ambulacral designations; An, anus; g, gonopore; h, hydropore; M, mouth. Plate colours and dashed outline of peristome and facets standard for following diagrams. Not to scale.