. Bulletin - United States National Museum. Science. 106 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. posterior branch, the latter, of the posterior branch of l!. em. Fig. 97.—Iasis zonaeia, aggregatedzooid, dorsal view. x 3 diameters. (drawn bt Hoyt S. Hopkins.) sphincter complex is reduced; the. dorsal portion reduced. Tho condition of the oral m viduals anions; mv material though short, probably the homolog io last body muscle in the aggregated zooids of other species. The intermediate muscle is well de- veloped ventrally, extending as near to the mid-ventral line as do the body muscles, bu
. Bulletin - United States National Museum. Science. 106 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. posterior branch, the latter, of the posterior branch of l!. em. Fig. 97.—Iasis zonaeia, aggregatedzooid, dorsal view. x 3 diameters. (drawn bt Hoyt S. Hopkins.) sphincter complex is reduced; the. dorsal portion reduced. Tho condition of the oral m viduals anions; mv material though short, probably the homolog io last body muscle in the aggregated zooids of other species. The intermediate muscle is well de- veloped ventrally, extending as near to the mid-ventral line as do the body muscles, but dorsally it passes but a little way beyond the angles of the mouth. Streiff interprets the inter- mediate muscle as double, an interpre- tation which seems to be borne out by comparison with some species still to be described. The oral musculature (fig. 99) shows a short oral retractor, which gives rise, at the angle of the mouth, to a wide admarginal sphincter muscle in each strongly incurved lip. Across the angle of the oral siphon lies a band of dark- colored muscle, comparable to that seen in a similar position at the distal end of the oral siphon in the solitary form of this species. Comparisons, especially with the C}7closalpas, will show how various are the interrela- tions of the intermediate muscle and the more basal sphincters of the lips, especially the upper lip. In several species the ventral portion of this Iasis hexagona, on the other hand, has usculature, in the very numerous indi- , is considorablv different from that. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States National Museum; Smithsonian Institution; United States. Dept. of the Interior. Washington : Smithsonian Institution Press, [etc. ]; for sale by the Supt. of Docs. , U. S. Govt Print. Off.
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