Gymnobeta has here been used in a wide sense, for species with a rather short and broad shell, often with shouldered whorls and rather strong sculpture. The surface of the shell is dull (cf, Theta, where the shell is more or less polished), and usually the shell is rather solid. The animal sometimes has eyes, an operculum is always lacking. The radular teeth have a rather uniform shape and the basal part is very similar throughout the species here placed in Gymnobeia. All the species known to us have a planktotrophic larval development, and a medium-sized larval shell with rounded whorls and oblique, cancellate sculpture.
The species of the group are not always easy to separate and identify, as they are sometimes quite variable and resemble each other. The larval shell is a good aid for the determination as also the presence of colour on the columella or other colour markings. Some of the more important characteristics are summarized below.
G. fulvotincta: columella usually reddish or brownish, never colourless. Whorls more or less angulated, sculptured by an even spiral sculpture below the subsutural zone. Axial sculpture only knobs at the periphery, which usually are present on the body-whorl.
G. emertoni: columella sometimes coloured, sometimes (in deep-water specimens) colourless. The sculpture consists mainly of spiral ribs of unequal size. Upper whorls more or less keeled, lower ones evenly rounded. Sometimes axial knobs on the upper whorl. These two species should not be confused with Xanthodaphne spp. which have more rounded and swollen whorls. G. agassizi: has a red-spotted columella, a very broad and solid shell, with low, broad axial ribs and irregular spiral sculpture.
G. abyssorum: shell light brown — brownish white. The sculpture consists of short, low and broad axial ribs and a spiral sculpture of rather equal-sized spiral lines. It is much more distinctly shouldered than G. agassizi.
G. pyrrhogramma: the shell is covered by irregular brownish axial spots; the shell is high and distinctly shouldered. The sculpture consists of equal-sized spiral ribs and close set, rounded axial ribs.
G. phyxanor: the shell is thin and pinkish brown. The whorls are rapidly increasing and sculptured with spiral lines and more distinct, rather close set, short axial ribs giving a reticulate appearance to the upper whorls.
G. lamyi: the shell is colourless and has a distinctly reticulated sculpture. The whorls are very rapidly increasing and distinctly shouldered.
G. leptoglypta: the shell is high and slender, the whorls evenly rounded; the sculpture is more or less distinctly reticulated on the lower whorls, the axial sculpture dominates on the upper whorls.
G. chyta: the shell is white, high and sharply shouldered. The ribs are less close set, compared with G. pyrrhogramma and the spiral sculpture more distant and irregular.
G. subaraneosa: has a colourless shell, very thin and fragile, sculptured with low axial ribs and fainter spiral lines and one spiral keel at the shoulder. Sometimes the sculpture is very faint, but usually the keel remains. The whorls are rather rapidly increasing.
G. frielei: shell white or greyish colourless. It is rather high and the shape a little reminiscent of that of G. agassizi, but that species has more angulated whorls; it is also smaller than that species and has more close set, higher and more curved axial ribs.
G. watsoni: shell sometimes a little greyish brown, to colourless. It is a small species, with a decussated sculpture with a faintly spiny appearance. The larval shell is much smaller than in G. aquilarum, the young of which it resembles.
G. engonia: a rather short and stout species with distinctly angulated whorls and a rather sharp sculpture. The shell is much thinner than in G. abyssorum and G. agassizi, which have a solid shell. The subsutural zone is more concave than in G. watsoni, which it might resemble.
G. aquilarum: shell small, short, very stout, of a dull greyish or whitish colour. The sculpture consists of rounded axial ribs and narrow incised V-shaped lines, which sometimes are broader and channelled. The apex is usually eroded.
G. homeotata: shell thin, pinkish brown. Whorls distinctly shouldered, sculptured by spiral lines and broader, oblique, short axial ribs.
Some turrid genera resemble Gymnobela very much in shell morphology viz. Marshallaria Finlay & Marwick, 1937, Acamptogenotia Rovereto, 1899, Belophos Cossmann, 1901, Belatomina Powell, 1942, Mioawateria Vella, 1954, etc. These genera were based on fossil species and are now for various, rather doubtful, reasons placed in different groups of Turridae. Such an arrangement certainly does not facilitate the understanding of variation in the family but rather increases the difficulties, by forcing the student to select and discard all erroneous information.