Spondylus chiriquiensis Olsson, 1922
OLSSON, A. A.. 1922. The Miocene of Nothern Costa Rica with notes on its general stratigraphic relations. Bulletins of American Paleontology, 9 (39): 177-481, pls. 1-32. [p. 378, pl. 20, figs. 1, 2, 5, 6]
1922 Spondylus chiriquiensis Olsson, 1922
A. A. Olsson, 1922, plate 20.
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«Shell large, ponderous, equivalve and strongly convex; both valves of the same convexity but with the beak of the right, high and projecting above the strongly incurved beak of the left; in large shells both valves are provided with a cardinal area, that of the right being both high and wide and for the greater part straight but the beak curving over it to a small extent at its upper end; the cardinal area of the left vale is much smaller, narrow and appears only with maturity and is more or less hidden by the strongly incurved beak; the sculpture consists of strong radial cords and small ribs divisible into 3 sets; a primary set of 7, which in perfect specimens and in the young carry large, strong spines; a secondary thread in each of the wide interspaces and when perfect bearing smaller spines, and tertiary threads of a variable number between the secondaries and primaries; the whole surface is in addition, finely longitudinally starited with minute, scale-bearing threads; young shells have a small foliaceous area on the umbo of the sessile or right valve and strong spines on both valves.
Height 151, length 120, diameter 115 mm. A large, ponderous species with nearly equal and strongly convex valves which show no distortion due to attachment. Young shells associated with the type have a small, somewhat foliaceous attachment area on the right valve, and each valve bears large, strong spines on its primary set of radial cords and finer spines on its secondary and even on some of the tertiary threads. Of described species, the chiriquiensis seems nearest related to the bostrychites Guppy from the Miocene of Santo Domingo and Jamaica but differs by its much larger size, proportionately more convex whorls and by its cardinal area which is more upright and with a more incurved beak at its upper end. The sculpture of chiriquiensis is more spiny, the spines being borne by the primary radials and to a less degree by the secondaries, and even by the tertiaries. In bostrychites only the primaries bear spines, the others appearing as large, nearly smooth, intermediate threads and cords. We have specimens of a large, closely allied Spondylus from the Chesapeake Miocene of Florida, differing mainly in its cardinal area and in details of sculpture. Gatun Stage: Water Cay.» AXEL ADOLPH OLSSON, 1922
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