Streptochetus, Cossmann, 1889

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 137

Streptochetus ? sp. B

Figs 30 P–Q

Material. A single nearly complete external mould. MGUH 33254 consists of the protoconch and initial six teleoconch whorls collected south of Højerup, Stevns Klint.

Occurrence. The Cerithium Limestone Member south of Højerup, Stevns Klint.

Description. Protoconch obtusely conical, consisting of two smooth whorls with distinct sutural angle; initial whorl small, not inflated.

Teleoconch high-spired, consisting of moderately convex whorls; whorls low, their height corresponding to nearly half their width. Narrow suture located in distinct angle between succeeding whorls, and bordered by weak subsutural collar. Aperture unknown.

Teleoconch sculpture dominated by around 10 strong, rounded transverse ribs partly aligned from whorl to whorl. Ribs giving the whorls a more convex outline. Interstices more or less equal in width to ribs. Spiral riblets strong and sharp, numbering around six. Transverse ribs fading out at transition to base, which is dominated by close lying spiral riblets, becoming gradually finer towards canal.

Measurements. Specimen, MGUH 33254 is more than 6.5 mm high and 2.6 mm wide, consisting of the protoconch and initial six teleoconch whorls. Exposed part of protoconch is 0.6 mm wide and 0.4 mm high.

Remarks. Streptochetus ? sp. B differs from Streptochetus sp. A described above from the same beds by the more opisthocline transverse ribs and the weak subsutural collar.

Figures

FIGURE 30. A–B. Amaea sp.A. Details of protoconch on external mould of MGUH 33242 shown in natural view and mirrored with inverted colours. Width of protoconch 0.6 mm. C–D. Amaea sp. B. C. Silicone cast of protoconch MGUH 33243. Width 0.6 mm. D. Silicone cast of protoconch MGUH 33244. Width 0.4 mm. E. Amaea? sp. C, Silicone cast of ØSM.10042-373. Width 5.5 mm. F–G. Acirsa torensis n. sp. F. Silicone cast of holotype MGUH 33245. Width 0.8 mm. G. Silicone cast of paratype MGUH 33246. Width 1.1 mm. H. Acirsa sp., Silicone cast of MGUH 33247. Height 6.2 mm. I–K. Opaliopsis carlsbergi n. sp. I. Silicone cast of holotype MGUH 33248. Height 2.2 mm. J. Silicone cast of paratype MGUH 33249. Height 1.7 mm. K. Silicone cast of paratype MGUH 33250. Height 3.0 mm. L–M. Fusinus schnetleri n. sp. L. Silicone cast of holotype MGUH 33251. Height 23.9 mm. M. Silicone cast of paratype MGUH 33252. Height 13.4 mm. N–O. Streptochetus sp. A. Silicone cast of MGUH 33253. Width of figure N 2.7 mm. Width of teleoconch 3.5 mm. P–Q. Streptochetus? sp. B. Silicone cast of MGUH 33254. Teleoconch width 2.6 mm.Width of protoconch 0.6 mm. R–T. Latirulus? sp. R–S. Silicone cast of MGUH 33255. Width of protoconch 0.7 mm. Height of teleoconch 10.5 mm. T. Silicone cast of MGUH 33256. Width 3.7 mm. U–W. Dolicholatirus lorenzi n. sp. U. Silicone cast of holotype MGUH 33257. Height 30.8 mm. V–W. Silicone cast of paratype MGUH 33258. Width of teleoconch 5.5 mm. Width of protoconch 0.7 mm. X. Vexillum tenestolidum n. sp., Silicone cast of holotype MGUH 33259. Width of teleoconch 4.3 mm.