Parvamussium inversum (Nilsson, 1827)
NILSSON, S. 1827. Petrificata suecana formationis cretaceae, descripta et iconibus illustrata a S. Nilsson. Pars prior, vertebrata et mollusca sistens. Londini Gothrum, Ex Officina Berlingiana. viii, 37 p., pls. 1-10. [p. 24, pl. 9, fig. 18a-b]
1827 Pecten inversus Nilsson, 1827
1842 Pecten squamula var. octosulcatus Geinitz, 1842
1850 Pecten subsquamula Orbigny, 1850
1842 Pecten squamula var. octosulcatus Geinitz, 1842
1850 Pecten subsquamula Orbigny, 1850
S. Nilsson, 1827, plate 9.
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«P. testa pusilla orbiculari, extus laevissima, intus costis 12-16 distantibus radiata, margine laevi; auriculis inaeequalibus, latis. Diam. 4-6 mm. (Tab. nostra IX. fig. 18. A. B. magnitudine naturali; scil. A. extus, B. intus; C. magnitudine aucta, intus).
Obs. Ad Pectinem squamulam Lam. Hist. anim. s. vert. VI. I. p. 183. & Annales du Mus. VIII. p. 354. proxime accedere, sed costarum numero majore differre videtur.
Descript. Testa minima, orbicuiaris, extus tota laevis, intus vero 15-16 costis compressis radiantibus, ante marginem testae desinentibus, ornata. Auriculae latissimae, ita ut margo cardinalis & latitudo testae fere aequales sint.
Locus: Ad Svenstorpsmölla, & ad Kopinge in arena viridi atque in calce arenosa & carbonifera haud raro.» SVEN NILSSON, 1827
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«No other Upper Cretaceous European species can be compared to P. inversus. From the Upper Cretaceous of Jordan I saw several specimens of Propeamussium samariensis (CONRAD, 1852) (B. M. L 67450, 67462 from Djenin) which are very similar to P. inversus NILSSON; they have 8-12 internal ribs, large unequal ears, a very long straight hinge-line which are also P. inversus characteristics. Between the ribs they seem to have very close concentric ornamentation which I do not known on P. inversus.
From the Paleocene of Copenhagen and from the Calcaire d'Eysden superieur in Eysden (Limburg, Belgium) a species which resembles the Cretaceous species has been described: Propeamussium (Parvamussium) bisculptum (VON KOENEN, 1885). The ribnumber is almost the same as in P. inversus but the other characteristics are different: in P. bisculptum the exterior of one of the valves bears a radial and a concentric ornamentation. Unlike Entolium and Syncyclonema which die out at the Cretaceous-Paleocene boundary Propeamussium crosses that boundary and seems to be hardly affected by it.» DHONDT, A. V. 1971. Systematic revision of Entolium, Propeamussium (Amusiidae) and Syncyclonema (Pectinidae, Bivalvia, Mollusca) of the European Boreal Cretaceous. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, 47 (32): 1-95, pls. 1-4. [p. 40]
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