Shell elongated, slender and conical, reaching 6.0 mm in length, 1.1 mm in width. Protoconch wide, with 2.5 to three whorls, first whorl dome shaped or somewhat pointed; first whorl with zigzag spiral cords of varying expression, sometimes smooth or irregular, but threads always well spaced; second whorl with axial riblets varying in number and arrangement (curved or straight), and with one or two spirals cords. Teleoconch with up to 10 convex whorls; four spiral cords, with the adapical one being smaller and less nodulose; ~13 axial ribs on the eighth whorl, forming nodules of medium or even reduced size on intersections with the spiral cords; an additional small cord at suture; last whorl with strong and slightly irregular subperipheral cord; base short and concave; aperture almost round, with short siphonal notch; outer lip thin; columellar lip sinusoidal. Protoconch and teleoconch usually with equal tonalities of brown, light brown, beige and white.

Distribution: Texas, Gulf of Mexico; Caribbean; Bermuda. Size: 7 mm
Description: Color crystalline tannish-white; shape tall, narrow, conic; sculpture of 3 spiral beaded rows on each whorl; beads connected axially and spirally by small rounded riblets; protoconch with fine spiral threads, followed by axial threads in area between protoconch and teleoconch; first postnuclear whorl with 2 spiral threads; latter whorls with 3 spiral ridges connected by axial riblets, producing a beaded appearance on each whorl, which extend to the base; aperture subcircular; small siphon; shell dextral. Habitat: Tropical calcareous environments at depths from 0 to 128 m (420 ft). Remarks: Similar to M. excelsa, but narrower with a reduced protoconch. Dextral form of triphorid. See Ode (1989b); Redfern (2001).

Metaxia rugulosa and M. excelsa are similar in the shell shape and the sculpture pattern of the teleoconch. The main differences consist of the protoconch shape, which is slenderer in M. excelsa and wider in M. rugulosa, and the number of whorls of the protoconch (~4.5 in M. excelsa, ~2.75 in M. rugulosa). In addition, the teleoconch of M. rugulosa is less shouldered, with smaller nodules, and has a more nodulose subsutural cord. Metaxia rugulosa exhibits variation in shell color, from white to brown. In contrast to the observations of ROLÁN & FERNÁNDEZ-GARCÉS (1992, 2008), who described only white shells, and LEE (2009), who obtained a majority of white shells and a minority of homogeneously brown ones, the shells from Brazil are brown in most cases, with a few white shells. ROLÁN & REDFERN (1996) provided a detailed study of the protoconch variation in M. rugulosa.

Metaxia propinqua Rolán & Fernández-Garcés, 2008 is a very similar species, with minor differences in the protoconch sculpture, i.e., the presence of axial riblets only above the first spiral thread of the second whorl of the protoconch of M. propinqua, whereas the axial riblets of M. rugulosa run from the entire second whorl of the protoconch. However, this difference appears to be included in the variation described by ROLÁN & REDFERN (1996) for the protoconch of M. rugulosa. Some of the shells from Brazil show axial riblets only above the upper spiral thread of the second whorl of the protoconch, but these shells are herein considered as included in the variation of M. rugulosa.

Another very similar species is Metaxia carinapex Linden, 1998, which is restricted to localities around the Cape Verde Archipelago. The teleoconch of M. carinapex is very similar to M. rugulosa, and its protoconch morphology seems to be included on the variation of M. rugulosa. A possible synonymy and consequent Atlantic distribution demands further study.

Shells of M. taeniolata without a protoconch may be similar to white shells of M. rugulosa that also lack a protoconch, but M. taeniolata has well pronounced nodules on the intersections of the spirals with the axial lines. In addition, M. rugulosa never develops a light brown spot in the internodular spaces of the second spiral row.

Geographic distribution. Bermuda (ABBOTT 1974, JENSEN & PEARCE 2009), USA: Florida (CAMP et al. 1998, LEE 2009), Louisiana (ROSENBERG 2009), Texas (TUNNELL JR et al. 2010); Gulf of Mexico (ABBOTT 1974), Bahamas (REDFERN 2001), Cuba (ROLÁN & FERNÁNDEZ-GARCÉS 1992), Jamaica (type locality), Costa Rica, Panama, Colombia (ROSENBERG 2009), Aruba, Bonaire and Curaçao (ABC Islands) (JONG & COOMANS 1988); Brazil: Pará, Abrolhos Archipelago, Bahia to Rio de Janeiro (this study).