Syncyclonema haldonensis (H. Woods, 1902)
WOODS, H. 1902-1903. A monograph of the Cretaceus Lamellibranchia of England. Vol. I. Paleontological Society Monograph. Part IV Pectinidae, pp. 145-196 (1902); Part V Pectinidae (continued), pp. 197-232 (1903). The Paleontographical Society (First reprinting, 1975: Vol. 56 nº 264 and Vol. 57 nº 267) [p. 151, pl. 27, fig. 4]
1902 Pecten (Syncyclonema) orbicularis var. haldonensis H. Woods, 1902
H. Woods, 1902-1903, plate 27.
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«4. Upper Greensand.— The forms from Ventnor are noteworthy for the large size which they reach; the number of concentric ribs is variable, and on the largest specimens the later part of the valve (Pl. XXVII, fig. 7 a) is smooth and without ribs, and in the ribbed part two distinct stages may sometimes be noticed, an earlier with close-set ribs, a later with more widely separated ribs (Pl. XXVII, figs. 8, 9). Sometimes the grooves are widely spaced and the ribs broad (fig. 9 a).
P. orbicularis seems to be rare at Blackdown, and the forms seen are rather small, with numerous ribs. The examples from the Chert Beds of Haldon (Pl- XXVII, fig. 4), of which there is a good series in the Exeter Museum, have the ears much larger thaan usual, also a smaller apical angle, and straight antero- and postero-dorsal margins; the shell is rather high in proportion, and the ribs are numerous. Since all the Haaldon specimens agree in these respects, and are readily distinguishable from those found elsewhere, they may be regarded as a local variety, and named P. orbicularis, var. haldonensis: this variety resembles the form from the Cenomanian of Bavaria figured by Söhle (1897). The forms found in the Upper Greensand of Warminster are rather larger than most of those in the Gault and Lower Cretaceous, and often have numerous ribs.» HENRY WOODS, 1902
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