9). There were probably radial muscles and muscles of the enteric canal and tentacles, but these have not been observed.
Radial canals.—The system of radial canals is very striking, and medusa-like. They radiate from a central ring canal (cr) out to the margin of the umbrella. The tube-like character is probably best
 Fig. 5.—Eldonia ludwigi, ✕ 2. A specimen flattened in the shale and preserving the alimentary canal, oral aperture and tentacles, water vascular system and traces of the umbrella. U. S. National Museum, Catalogue No. 57537. ul = umbrella lobes crushed and macerated; cr and rc = central ring and radial canals of vascular system; o = oral aperture; tt = peltatodigitate tentacles; oc = oral chamber; œ = œsophagus; s = stomach; I = intestine; x = approximate point of union of stomach and intestine. The latter is better shown by fig. 2, pl. 10; and figs. 1 and 2, pl. 12. |
shown by fig. 3 of pl. 11. They are usually crushed down with the alimentary canal and all traces there lost, but in several examples some of the canals may be traced across the broad canal and out on the disk beyond. On a few specimens (pl. 8, fig. 3) some of the radiating canals merge into rings that line the inner side of the margin of the alimentary canal. On the outside of the alimentary canal in this specimen the flattened radial canals appear like narrow ribbons or bands united by fine fibers that may be traces of concentric muscles. Where the outer margins of the umbrella have been macerated
