Propeamussium dalli (E. A. Smith, 1885)
SMITH, E. A. 1885. Report on the Lamellibranchiata collected by H.M.S. Challenger during the years 1873-76. In Report on the Scientific Results of the Voyage of H.M.S. Challenger during the years 1873-1876. Zoology, 13: 1-341, pls. 1-25 [p. 308, pl. 22, figs. 7-7c]
1885 Amussium [sic] dalli E. A. Smith, 1885
E. A. Smith, 1885, plate 22.
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«Testa tenuissima, compressa, hyalino-albida, aequivalvis, elongata. Valvae sculptura diversa ornatae, altera (? dextra) conspicue nitente, incrementi lineis striisque tenuissimis sculpta, altera liris concentricis tenuibus ornata, undique minutissime cellulosa. Auriculae parvae, subaequales, utrinque acute angulatae, in valva dextra lateribus paulo concavis. Pagina interna fulgens, liris undenis radiantibus albis hand ad marginem productis instructa.
This species is longer from the beaks to the lower margin than from side to side. It is almost equivalve, the smoother valve, which I regard as the right, being perhaps a trifle more swollen than the other. It is a very thin fragile shell, semitransparent and very glossy, particularly the right valve, which has a more glossy appearance than the left, the latter being of a somewhat thicker texture and of a dilute milky white colour. The valves are differently sculptured. The right merely exhibits the fine concentric lines of growth and very fine radiating substrise. The left is more beautifully ornamented, being concentrically closely and finely lirate, and throughout microscopically shagreened, the outer or surface-layer being composed of countless excessively minute closely packed crystal-like bodies having unequal sides, varying in number from four to six, and flat outer and basal surfaces. The beaks are acute, and converge to an angle of about 110 degrees. The ears are small, about equal on both sides, slighty concave laterally in the right valve. The interior is very glossy, strengthened by eleven fine radiating costellae, which, with the exception of the two very short uppermost, only extend about half-way across the surface of the right valve, and rather further in the left, in which also they are a trifle thicker.
Length 48 mm., height 52, diameter 8. Habitat.— Station 33, off Bermudas, in 435 fathoms; coral mud. This fine species is dedicated to Mr. W. H. Dall as a mark of high esteem on account of his many and valuable papers on malacology.» EDGAR ALBERT SMITH, 1885
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