Plectostoma grandispinosum (Godwin-Austen, 1889)
Godwin-Austen (1889) original descriptions on Opisthostoma grandispinosum – “Shell dextral, depressedly pyramidal, thin, glassy, transparent sculpture smooth, with lines of growth; the periphery, the upper whorls, and the extended free portion of the last whorl are set with curved, white, glassy spines, the largest nearest to the aperture; each spine rises from a fine transverse rib, above and below the whorl, these nearly meeting, a gutter-like fold is produced which rises at right angles with the whorl; colour pale amber or sienna-brown, with a golden lustre; spire moderately high, conic, sides convex; apex rather sharp; suture impressed; whorls 5 to the constriction, whence it leaves the adjacent whorl, and turns sharply at right angles upwards in a diagonal direction to the apex of the shell, lying closely to the spire, reaching the apex it takes another sharp turn to the aperture, which thus rises high above and clear of the apex; aperture widely circular, trumpet-shaped; peristome continuous, thin, simple.”
Kobelt (1902) descriptions on Opisthostoma (Geothauma) grandispinosum – “Schale rechtsgewunden, niedrig kegelförmig, dünn, glasartig, glatt, in der Mitte der oberen Windungen und am freien Teil der letzten mit aus Rippen entspringenden, nach der Mündung hin grösser werdenden, weissen, glasartigen, gebogenen Stacheln besetzt, gold-bernsteinfarben; Gewinde massig hoch, gewölbt kegelförmig, Apex spitz; 6 Windungen, letzte nach der Einschnürung plötzlich nach oben gerichtet und bis zum Apex emporsteigend, dann wagerecht, völlig abgelöst; Mündung weit, kreisrund, trompetenfönnig; Mundrand zusammenhängend, dünn, einfach.”
By Vermeulen (1994)
"Spire conical with distinctly convex sides. Apex (slightly) oblique. Whorls 4 3/8 - 4 7/8; top whorls convex; last whorl obtusely angular at the periphery, slightly convex above and below. Constriction with a short and inconspicuous parietalis, a transverse palatalis, an inconspicuous columellaris. Tuba bulging and then abruptly narrowed towards the constriction, slightly angular below. Radial ribs widely spaced (1-2 ribs/0.5 mm on the penultimate whorl and half-way on the tuba), those on the spire hardly visible but on the lower half of the whorls with a deeply trough-shaped to almost tubular, slightly curved projection, abrading to a scar with a single deep loop; those on the tuba similar but more distinct, with longer, strongly curved projection below which is swollen at the tip. Spiral striation absent. umbilicus open, 0.35-0.50 mm across. Aperture tilted up to 20 degrees with regard to the coiling axis, its upper margin widely above the level of the apex, elliptic. Peristome distant from the spire, double; outer peristome hardly to moderately spreading beyond the inner all around, or sometimes graduallu narrowed towards, and absent along the side of the aperture which is closest to the spire; inner peristome not or hardly protruding from the outer, spreading. Spire: height 1.9-2.2 mm; width 1.7-2.0 mm; index 1.0-1.1. Total width 2.8-3.1 mm. Height aperture 1.4 mm; width 1.1 mm."
Opisthostoma grandispinosum – “Size: maj. diam. 2.4 mm; alt. axis 1.9 mm; length of longest spine 1 mm.” (Godwin-Austen, 1889); Opisthostoma (Geothauma) grandispinosum – “H. 1.9, Durchm. 2.4 mm.” (Kobelt, 1902)
Type locality – “Niah Hills” leg. A. Everett (Godwin-Austen, 1889);