Spondylus olssoni Clark in Clark & Durham, 1946
CLARK, B. L. & J. W. DURHAM. 1946. Eocene Faunas from the Department of Bolivar Colombia. Geological Society of America Memoirs, 16: 1-126, pls. 1-28 [p. 55, pl. 3, figs. 1, 5, 6; pl. 4, figs. 1, 6]
1946 Spondylus olssoni Clark in Clark & Durham, 1946
B. L. Clark & J. W. Durham, 1946, plate 3, figures 1, 5, 6; plate 4, figures 1, 6.
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«Shell inequilateral, inequivalved; left valve with broader apical angle than that of right and not so high; right valve with large smooth triangular cardinal area below beak, a little more convex than left and with more strongly depressed and wider dorsal margins; surface sculptured by about 46 angular-topped radial ribs separated by narrow V-shaped interspaces; several ribs bifid; these are inthe area about half way between the dorsal-ventral medium line and the posterior end; ribs on depressed dorsal margins less distinct than on main surface of shell; ears well developed, with their upper dorsal edges which bound the broad cardinal area sloping obliquely away from beaks, anterior ear being narrower than posterior; both sculptured by fine radial ribs, about 6 on the posterior ear and about 4 on the anterior ear; on main surface, radial ribs crossed by sharp Jamellalike incremental lines; surface of left valve sculptured by about 38 radial ribs similar to those on right valve except that several of these are heavier than any of the others and appear to have been spinose; this is best seen on the paratype (pl. 4, fig. 6); upper dorsal edges of fairly large equal ears form straight line similar to that seen on the genus Pecten; radial ribbing on ears not so well developed as on those of right valve; upper dorsal portion of ear apparently smooth, while on ventral portion there is 1 fairly heavy rib on anterior ear and 2 on posterior ear; hinge plate not exposed. Dimensions of holotype, U. C. Loc. S 8049, spec. no. 34916: length 74 mm., height of right valve about 77 mm., height of left valve 70.8 mm., maximum thickness including both valves about 43 mm.; of paratype, same locality, spec. no. 34917: length about 68 mm., height of right valve about 71 mm., height of left valve about 69 mm. (ventral margin broken), thickness, both valves included, about 36 mm.; of paratype, U. C. Loc. S 7334, spec. no. 34876: height about 66 mm.
The above description is based upon the holotype; neither of the paratypes is so well preserved, the ventral edge being broken. The surface of the right valve of the paratypes is more eroded than that of the holotype and shows the ribs arranged more in pairs, though there is a suggestion of this on the holotype. On the paratype the ribs are terraced on their sides; this character is not seen on the holotype apparently because the terraces are covered by the coarse incremental lines.» BRUCE LAWRENCE CLARK, 1946
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