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Species / Monalaria Gracilis


Original Description of Monalaria gracilis by Finlay & Marwick, 1937, p. 106:

  • "Shell rather small, slender, spire not so high as the aperture. Early whorls convex, later ones angled, with a moderately inclined shoulder, body-whorl with a strong shoulder-angle and a double keel, the lower cord of which is weaker than the upper. Between the shoulder-angle and the keel the shell is slightly concave, and the base is contracted with slight concavity to the beak. Sculpture: the early whorls have short curved axial ribs on the upper part, crossed by spaced spiral cords. The ribs terminate about the middle of the side, and below them is a slight concavity, followed by the upper keel, which seems to have been clear of the suture. The sculpture at this stage is closely similar to that of Struthiolarella. On the later, angled whorls, the shoulder bears weak, but somewhat sharp, tubercles, produced as low oblique axials down the side, and the double keel also bears tubercles. The spiral sculpture consists of fine, well-spaced, sharp, spiral threads, about 15 on the side of the body-whorl, 6 very fine ones in the shoulder angle, 2 or 3 on each keel, 3 between them, and 17 showing on the base, near the inner lip, the upper 8 of these alternating in strength. Aperture elongately oval. Outer lip not preserved, but probably thickened and reflexed, with a broad sweeping sinus above, and strongly convex at the keel. Inner lip with a moderate callus. Columella long and sinuous."

Dimensions:" Height (estimated), 22 mm.; diameter, 12 mm. Paratype, 18 mm. by 8 mm."

Locus typicus: "Castle Hill Shaft" at Kaitanga, South Island, New Zealand

History and Synonymy


Marwick defined Monalaria gralis filata

Monalaria gracilis filata Marwick, 1960; Cast of holotype; Lower Eocene; Otaio Gorge, Canterbury, South Island, New Zealand; Copyright BM(NH)

Monalaria gracilis filata Marwick, 1960; Cast of paratype; Lower Eocene; Otaio Gorge, Canterbury, South Island, New Zealand; Copyright BM(NH)

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