Spondylus spinosus (J. Sowerby, 1814)
SOWERBY, J. & J. DE C. SOWERBY. 1812-1846. The Mineral Conchology of Great Britain; or coloured figures and descriptions of those remains of testaceous animals or shells. 7 vols., pls. 1-648 (and 2 bis). London [vol. 1, p. 177, pl. 78, figs. 1-3]
1814 Plagiostoma spinosa J. Sowerby, 1814
1822 Plagiostoma brightoniensis Mantell, 1822
1835 Spondylus duplicatus Goldfuss, 1835
1858 Spondylus aequalis Hébert, 1858
1860 Spondylus subspinosus Coquand, 1860
1822 Plagiostoma brightoniensis Mantell, 1822
1835 Spondylus duplicatus Goldfuss, 1835
1858 Spondylus aequalis Hébert, 1858
1860 Spondylus subspinosus Coquand, 1860
J. Sowerby & J. de C. Sowerby, 1812-1846, plate 78.
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«SPEC. CHAR. Obovate, longitudinally furrowed; sides nearly equal, straightish; one valve spinous, spines half the length of the shell.
One valve is more convex than the other, the flatter one being spinous; both are deeply and regularly furrowed both outside and within, the projections of the inside terminate in angular teeth near the edge. The spines, in number about twenty-five, are largest near the front of the shell; at the sides they are smaller and lie closer together: each spine has a dorsal ridge and a distinct furrow beneath. Beaks projecting. The whole surface of the shell is covered with very fine transverse projecting strias; the lines of growth sometimes interrupt the regularity of the furrows, and the spines are sometimes very short and adpressed, at others they are irregularly bent, but their general position is at an angle of about 45°, with the shell. The breadth is rather above two-thirds of the length. I can discover no muscular impression within the shell, although I have specimens perfectly cleared from the chalk.
This species is common both in the soft and hard Chalk, and is often attached to Flints. I have received it in hard Chalk from Mr. Mantell, found near Lewes; from Norton Bevant, Heytesbury, &c. from Miss Benett. Inside casts are common in gravel flints, these, of course, do not expose the spines. Mrs. Morris sent me a specimen picked up at Kickmansworth, and I have a cast in Calcedony, found near Sidmouth, for the possession of which I am indebted to the kindness of my friend Mr. Thomas. Its varieties are almost, nay sometimes quite, destitute of spines; Mr. Mantell sent me a specimen from Lewes, in which some of the spines are almost at right angles to the shell, and the others laying in bas-relief, curving in elegant tarns, as if too weak to rise. Fig. 1 represents the spinous side of a specimen said to be from Brighton, the Chalk is cut from it as far as might be to leave support to the spines; the beak of the plain side is just visible. Fig. 2 gives the dorsal view of a specimen from Northfleet, showing the triangular aperture: this specimen had the remains of a Flustra on some parts of it. Fig. 3 the inside of a detached spinous valve, having no appearance of a muscular impression, as in Pecten.» JAMES SOWERBY, 1814
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«Description. Ovate, slightly inaequilateral shell, rounded ventrally, and with prominent umbonal region. Valves may be equally convex, but normally the right valve is flattened owing to its attachment, which is achieved by means of irregular concentric frills. Right valve larger than left valve; strong radial ribs with a series of strong, long, tapering spines that are grooved on their upper surface. Left valve very convex, ornamented by strong radial ribs that occasionally develop spines; the juvenile shell may also have tuberculate spines on the rib crests. The spines on the right valve do not occur to a pattern, although the two most lateral series are usually the best developed and are evenly spaced around the commissure.
Remarks. Carter (1972) discussed the ontogeny of S. spinosus and interpreted its possible functional morphology and palaeoecology. Two extreme forms have been recognised: (1) aequalis-type, in which intermediate ribs are developed only near the margin of the left valve and, together with the well-marked and closely packed growth lines, give a frilled appearance to the shell. The ribs on the right valve are not divided, and spines occur on both valves (e.g. 'S . brightonensis' from the M. coranguinum Zone). (2) duplicatus-type, in which the left valve has many intermediate ribs and the ribs on the right valve have a narrow median furrow. Occurrence. Cenomanian, S. gracile Zone, to Late Campanian, B. mucronata Zone; common at most horizons and localities from the Dorset coast to Norfolk.» CLEEVELY, R. J. & N. J. MORRIS. 2002. Introduction to molluscs and bivalves. In A. B. Smith & D. J. Batten (Eds.): Fossils of the Chalk, 99-160. The Paleontological Association. London. [p. 129, 131]
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Spondylus spinosus (J. Sowerby); R. J. Cleevely & N. J. Morris, 2002, Introduction to molluscs and bivalves, plate 22, figure 1.
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