. Bulletin - United States National Museum. Science. 114 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. Mantle thin, not adherent to the test in preserved specimens ex- cept in the region of the apertures. Musculature very slight or almost wanting on most parts of the body, but slender bands radiate from the apertures and generally unite in groups to form larger bands. These, however, do not extend far from the apertures except those near the two angles of the mouth-like cleft. There the bands are long and stout and closely grouped, and serve to move the valve or cover. Tentacles simple, rather
. Bulletin - United States National Museum. Science. 114 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. Mantle thin, not adherent to the test in preserved specimens ex- cept in the region of the apertures. Musculature very slight or almost wanting on most parts of the body, but slender bands radiate from the apertures and generally unite in groups to form larger bands. These, however, do not extend far from the apertures except those near the two angles of the mouth-like cleft. There the bands are long and stout and closely grouped, and serve to move the valve or cover. Tentacles simple, rather small and widely spaced, about 32 in number of 3 orders rather regularly arranged; in addition there are a few fourth-order tentacles in some parts of the circle. (This count was made in one of the largest specimens.) Dorsal tubercle C-shaped with strongly incurved horns; the open interval directed Figs. 68-71.—Rhgdosoma papillosum (Stimpson). 68, External view. X GO, Dossal tubercle, part of dorsal lamina, and part of the circle of tentacles. X 10. 70, Part of branchial sac. X 15. 71, Stomach, part of intestine, and GONADS AS SEEN THROUGH MANTLE. X Dorsal lamina represented by a series of small, rather slender lan- guets. Branchial sac without folds or minute plications. Transverse vessels very numerous, of two sizes placed alternately in most parts of the sac, but in some places nearly uniform in size. The intervals between the transverse vessels are divided by very numerous slender longitudinal vessels into rather narrow stigmata. At intervals of 3 or 4 stigmata small curved papillae arise from the transverse vessels and support slender internal longitudinal vessels. They pro- ject a trifle^ beyond their point of union with the internal longi- tudinal vessels. The latter in large and old individuals are mostly incomplete and interrupted between the supporting papillae so that they form merely lateral branches of these papillae. (See fig. 70.) In one of
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
