Amusium toulae (Brown & Pilsbry, 1911)
BROWN, A. P. & H. A. PILSBRY. 1911. Fauna of the Gatun Formation, Isthmus of Panama. Part 1. Proceedings of the Academy of Natural Sciences of Philadelphia, 63: 336-373. [p. 365, pl. 28, fig. 7]
A. P. Brown & H. A. Pilsbry, 1911, plate 28.
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«Pecten (Amusium) gatunensis Toula, Jahrb., p. 716, PI. 26, fig. 10. Not Pecten gatunensis Toula, t. c, p. 711.
The shell is smooth, thin and flat, equilateral, closely resembling P. lyonii Gabb, of Sapote, Costa Rica (probably Miocene), and P. papyracea Gabb. of the Santo Domingan Oligocene. The surface is marked with narrow, sharply defined gray rays on a white ground, the rays less than half as wide as the intervals, subequal in the median part, much narrower at the sides, where they gradually fade out, and about 17 in number. Ears broad, subequal, marked with close, fine growth-lines, more distinct than on the disk. Interior smooth, so far as seen, but the marginal region, where ribs are developed in related forms, is wanting in the specimen. Greatest breadth of the broken specimen figured 48 mm. It attains a much greater size.
In P. lyonii the gray rays are wider, when visible, and the spaces between them are slightly convex; the interior has coarse radial ribs, but none are visible in P. toulae where the inside is exposed, at the lower margin of the broken shell. P. papyracea has fine internal ribs in pairs. Toula has figured and described this species, but by oversight he used a specific name already employed on a previous page of the same paper.» AMOS PEASLEE BROWN & HENRY AUGUSTUS PILSBRY, 1911
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