. The Crinoidea flexibilia (with an atlas of and 76 plates). Crinoidea, Fossil. 2Q2 SMITHSONIAN INSTITUTION CLEISTOCRINUS nov. gen. (jolaaTog, closed; xplror, lily) Plate XXXVIII, figs. 1-2. Fig. 37. Cleistocrinus Ichthyocrinidae with rays in contact except at anal side. Crown expanding" distally. Infrabasals entirely within the ring of basals, or wanting. Posterior basal not differentiated. Radianal in form of radial under right posterior radial. Anal x followed by others in series, usually not connecting with basal. Inter- brachials wanting. Primibrachs two. Arms unknown. Column
. The Crinoidea flexibilia (with an atlas of and 76 plates). Crinoidea, Fossil. 2Q2 SMITHSONIAN INSTITUTION CLEISTOCRINUS nov. gen. (jolaaTog, closed; xplror, lily) Plate XXXVIII, figs. 1-2. Fig. 37. Cleistocrinus Ichthyocrinidae with rays in contact except at anal side. Crown expanding" distally. Infrabasals entirely within the ring of basals, or wanting. Posterior basal not differentiated. Radianal in form of radial under right posterior radial. Anal x followed by others in series, usually not connecting with basal. Inter- brachials wanting. Primibrachs two. Arms unknown. Column large, cover- ing basals. Genotype. Calpiocrinus humilis Angelin. Distribution. Silurian, Wenlock Group; only known from Gotland. I have proposed this genus to receive a form which, although represented by rather imperfect material, is nevertheless of a very definite type, and occupies a place in the present family which cannot be confounded with any other. It is founded upon the Silurian species described by Angelin as Calpiocrinus humilis. His figures show very little of the essential structures which make the form important, and which are now clearly brought out by new figures made after further preparation of the specimens, especially by removal of the stem ossicles filling the basal cavity in one of them, thus enabling us to see the true arrangement of plates which was before obscured. This form stands close to Ichthyocrinus, but with the posterior rays partly separated by anal plates; as in that genus the posterior basal is not differentiated, but a strong series of anal plates is interposed above the level of the radials, one of which and the radianal meet below, entirely separating the anal series from the basal circlet. This is a very unusual structure in crinoids, but is found also in one species of Calpiocrinus; therefore I have not made it an absolute generic character, and a species with anal plate coming down to the basal would be admitted. The extreme diminution
Size: 1748px × 1429px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookpublishercityo, bookyear1920
