Douglassia curasub, Fallon, Phillip J., 2016

Fallon, Phillip J., 2016, Taxonomic review of tropical western Atlantic shallow water Drilliidae (Mollusca: Gastropoda: Conoidea) including descriptions of 100 new species, Zootaxa 4090 (1), pp. 1-363 : 136-138

Douglassia curasub , new species

(Plate 60)

Type material. Holotype 10.0 x 4.6 mm, C. Baldwin! aboard submersible Curasub , 8 Feb 2013 (USNM 1231397); 1 paratype from the type lot: 9.5 x 4.7 mm (USNM 1231398).

Type locality. Off Sea Aquarium, Bapor Kibra, Willemstad, Curaçao, Netherlands Antilles, 12°04'59.51"N, 68°53'56.61"W, in glass bottle collected at 800–900 ft [244–274 m].

Range and habitat. Known only from the type locality.

Description. Shell small (to 10.0 mm in total length), broadly fusiform, truncated anteriorly with a rapidly tapering spire and a disproportionately large last whorl, which is about 63% of total length; shell surface glossy; of up to 8¾ moderately convex whorls, the last contributing to the shell’s large average W/ L ratio of 0.477. Sculpture is of low ribs that are narrow on early whorls, broad on the last. Protoconch of 2¾ round glossy whorls with gradually increasing diameters, the first partially immersed in the second. Axial sculpture of ribs that extend from suture-to-suture on spire whorls and evanesce below periphery of last whorl; 8 ribs on penultimate and 5–6 to varix on last. Ribs narrow, slightly prosocline, and crests ridged on early whorls, broad, crests round and slightly opisthocline on last two. Coarse growth striae are present. Varix large, thick, cup-handle-like just behind the anal sinus within ¼-turn from edge of outer lip. Varix traces a nearly perfect circular arc from suture to anterior canal. Spiral sculpture absent. Sulcus absent; previous positions of the anal sinus are marked by ribs that are reduced, narrowed, and slightly recurved on whorl shoulders. Outer lip thin, narrow, juts out a short distance from the base of the varix; stromboid notch unknown, anterior edge of lip chipped. Anal sinus a short notch with a round apex and parallel sides. Inner lip margined, erect on anterior portion of columella, recumbent and thin on parietal wall, and developed into a lobe posteriorly at anal sinus. Anterior canal very short, barely formed, open; anterior fasciole not swollen, without spiral threads or grooves. Color light golden-brown; paratype with a thin, white spiral line below whorl periphery.

Remarks. Taxonomy. Douglassia curasub has some but not all the key characteristics of Douglassia —a cuphandle-like varix behind the anal sinus and a protoconch with 2¾ smooth round whorls. Ribs are present up to the suture, not greatly diminished in a sulcus as is typical of the genus, and curiously, it lacks spiral threads on the anterior fasciole and lower shell base, which are present on all other known members of the genus. Its coarse growth striae are also unique among its congeners, as is the rib pattern which changes from prosocline on spire whorls to opisthocline in orientation on the penultimate and last whorls. It quite probably represents a different, unnamed genus. Identification. Douglassia curasub is similar to D. antillensis , new species, D. enae Bartsch, 1934 , and D. moratensis , new species. From D. antillensis it differs in the following characteristics: a varix with a nearly a perfect circular arc, not one that straightens out anteriorly; ribs on the last two whorls that are lower, with rounder crests; an anterior fasciole that lacks spiral threads; growth striae that are coarser; a different color—almost entirely light golden brown; and smaller size. From D. enae it differs in all the same ways as it does from D. antillensis , and in addition, it has much less angular shoulders. From D. moratensis it differs in all the same ways as it does from D. antillensis in addition to being differently colored.

The two specimens are so distinctly different from any of its congeners and as such are unlikely to represent variants, so are believed to merit description as a separate species.

Etymology. The Curasub Douglassia . Named for the submersible that recovered an old, early 1880’s bottle containing the specimens described here.