Merklinia aspera (Lamarck, 1819)
LAMARCK,
J. B. 1819. Histoire naturelle des animaux sans vertèbres, présentant les
caractères généraux et particuliers de ces animaux, leur distribution, leurs
classes, leurs familles, leurs genres, et la citation des principales espèces
qui s'y rapportent. Tome
sixième, Premier partie, 343 p. Chez l'Auteur, au Jardin du Roi. De l'imprimerie de A. Belin. Paris, 1819. [p. 180]
1813 Pecten scaber Pulteney, 1813
1813 Pecten triplicatus Pulteney, 1813
1819 Pecten asper Lamarck, 1819
1813 Pecten triplicatus Pulteney, 1813
1819 Pecten asper Lamarck, 1819
M. Lister, 1688, Historiae Conchyliorum, plate 470, figure 28.
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«8. Peigne rude, Pecten asper.
P. testa suborbicuiari, utrinque convexa; radiis 20 ad 22 sulcis longitudinalibus divisis, imbricato-squamosis, scabris. List. Conch. t. 470, f. 28. Habite....... Fossile des environs de la Ferté-Bernard, département de la Sarthe. Mus. nº. Cabinet de M. Menard et le mien. Ce peigne semble être l'analogue fossile de notre P. asperrimus qui vit dans les mers de la Nouvelle Hollande. Largeur, 90 millimètres.» JEAN BAPTISTE LAMARCK, 1818
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«Diagnosis. — Merklinia-species covered· with 12-22 radial ribs, subdivided into many side-riblets with small scales or spines. At the apical margins well developed striated lunulate areas are present; the striae are perpendicular to the U. P. D. axis of the shell. Both valves are rather convex, the right valve rather more so than the left.
The ribs are angular and equal in shape on both valves; near the umbo they are undivided; further away from it side-riblets appear on the ribs; their number can reach five per rib side; on the valve, considered as a whole, there is no uniformity in this respect; all ribs are covered with spinules of different sizes and in varying number; on small valves these spinules are relatively larger than on larger valves; they are more scale-like than spine-like on right valves. The intercostal intervals are smooth, except for poorly developed concentric growthlines. On small valves the intervals are relatively broader than on larger valves, because on the former the ribs are undivided, whereas on the latter they are subdivided and thus the intervals seem narrower. Almost all auricles are right-angled; the anterior auricle of the right valve has a shallow byssal sinus; all auricles are covered with a varying number of radial, spinule bearing riblets. The lunulate areas are well developed and are as long as the apical margins; they follow the base of the auricles and end at the umbo. They are present at the anterior and posterior side of the shell and on both valves; the lunulate areas of the right and left valves are the reflection of each other and the striae which cover them seem to continue from one valve to the next. Discussion
Variability:
The ribnumber in Merklinia aspera is fairly variable; this can be explained partly by the difficulty there is in counting the ribs when they are strongly subdivided: side-riblets are, on some valves, almost as strongly developed as the principal ribs. Small specimens of M. aspera have almost no side-riblets: in the Musée géologique in Lausanne and in the Muséum d'Histoire naturelle in Geneva there are a few specimens which have only one side-riblet on each side of the principal ribs; on these specimens the spinules of the principal ribs are much more developed than those of the accompanying side-riblets or than those of principal ribs on larger valves. Synonymy: For Pecten scaber and P. triplicatus PULTENEY, 1813 see Cox, L. R. 1940 (p. 125). Apart from this, Merklinia aspera is such a typical species that no confusion has arisen in the literature. As for Pecten (Chlamys) saxonicus E. DACQUÉ non SCUPIN, it is difficult to reach a conclusion because the original specimen is a steinkern without trace of ribornamentation (2). Differentiation: It is easy to differentiate Merklinia aspera from the other Merklinia species, by the higher ribnumber of the former.» (2) Pecten saxonicus SCUPIN, 1913: the original of this species is a poorly preserved specimen kept in the Martin-Luther-Universität-Halle-Wittenberg, Halle an der Saale (G. D. R.).
DHONDT, A. V. 1976. Systematic revision of the Chlamydinae (Pectinidae, Bivalvia, Mollusca) of the European Cretaceous. Part 4: Merklinia. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, 51 (7): 1-38, pls. 1-2. [p. 11]
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Merklinia aspera (J. B. Lamarck, 1819); A. V. Dhondt, 1976, Systematic revision of the Chlamydinae of the European Cretaceous, Part 4: Merklinia, plate 1, figures 1a, 1b.
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