Mathilda malvinarum ( Melvill & Standen, 1907 )

Luca, Javier Di & Zelaya, Diego G., 2019, Gastropods from the Burdwood Bank (southwestern Atlantic): an overview of species diversity, Zootaxa 4544 (1), pp. 41-78 : 63

Mathilda malvinarum ( Melvill & Standen, 1907)

Fig. 5D

Cerithiopsis malvinarum Melvill & Standen, 1907: 135 , figs. 6, 6a; Strebel, 1908: 49, pl. 1, figs. 10a–c

Mathilda malvinarum — Powell, 1951: 113

Examined material. 10 sh. (MACN-In 40700).

Description. Shell height to 2.8 mm (up to 4 mm according to Melvill & Standen 1907); turritelliform, moderately solid. Protoconch large, of 1 markedly convex whorl; sculptured with 4 low, wide spiral cords. Teleoconch of up to 5.75 whorls, markedly convex in outline; last whorl comprising about 45% of total shell height. Suture impressed. Surface pale brownish, clearer at spiral sculpture; sculptured with 25 to 30 axial ribs per whorl and 4 spiral cords, the 2 adapical being stronger. Base delimited by a strong cord and sculptured with up to 9 additional, narrower cords. Aperture almost rounded, somewhat projected anteriorly, interior brownish with lighter margin; columellar callus narrow, slightly reflected.

Remarks. The original figure by Melvill & Standen (1907) only shows 2 spiral cords per whorl. However, Strebel (1908), who studied the same specimens, figured four spiral cords per whorl, a condition similar to that found in the material here examined.

Figures

FIGURE 5. A. Orbistestella ponderi Linse, 2002, MACN-In 40697, scale bar = 0.25 mm. B. Acteon biplicatus (Strebel, 1908), MACN-In 40698, scale bar = 1 mm. C. Neactaeonina argentina Zelaya, Schejter & Ituarte, 2011, MACN-In 40699, scale bar = 4 mm. D. Mathilda malvinarum (Melvill & Standen, 1907), MACN-In 40700, scale bar = 1 mm. E–F. Omalogyra burdwoodiana Strebel, 1908, MACN-In 40701, scale bar = 0.5 mm. E. Lateral view. F. Apical view. G. Odostomia sp. 1, MACN-In 40702, scale bar = 1 mm. H. Odostomia sp. 2, MACN-In 40703, scale bar = 1 mm. I. Odostomia sp. 3, MACN-In 40704, scale bar = 1 mm. J. Turbonilla strebeli Corgan, 1969, MACN-In 40705, scale bar = 1 mm. K. Diaphana paessleri (Strebel, 1905), MACN-In 40706, scale bar = 1 mm. L. Toledonia cf. elata Thiele, 1912, MACN-In 40708, scale bar = 1 mm. M. Toledonia cf. perplexa Dall, 1902, MACN-In 40707, scale bar = 1 mm. N. Toledonia sp., MACN-In 40709, scale bar = 1 mm.