Decoradrillia interstincta, 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 : 121-123

Decoradrillia interstincta , new species

( Plates 51 , Figs. 5, 6 & 55)

“Unnamed”: Williams (2005: species 9009) is this species (figured specimen is now the holotype).

Types. Holotype 12.0 x 4.3 mm, M. Williams! 28 Dec 1989, ex Williams coll. (USNM 1291337); 2 paratypes: 1 spec., 11.2 x 4.0 mm, in 23 m, on coral sand in surge channel, 7.2 km W of “Big Rocks”, Utila I., Bay Is., Honduras (ANSP 464986); 1 spec., 10.7 x 4.1 mm, in 37 m on soft sand, S coast of Helena I., 2.5 mi [4 km] E of Roatan I., Bay Is., Honduras, 16°25'36"N, 086°10'89"W (UF 496636); both paratypes R. Masino!

Type locality. On reef, Big Rock Reef, off the south coast of Utila I., Bay Is., Honduras, at 12– 18 m.

Range and habitat. Known only from the Bay Is., Honduras (Utila I.; Helena I.). All of the type specimens were dead-collected on sand near coral reefs between 12–37 m depths, which suggests a reefal habitat.

Description. Shell small (to 12.0 mm in total length), fusiform, truncated anteriorly, with a total of 8½ convex whorls, the last whorl approximately 52% of shell length; suture impressed, undulates over underlying ribs. Protoconch of 1½ smooth, glossy round whorls, the first not immersed in the second. Axial sculpture of strong ribs; crests narrower on shoulder, rounder on whorl periphery; spaces between ribs about as wide as the ribs; ribs run from suture-to-suture, are slightly arcuate on the whorl’s shoulder, run to the anterior fasciole on the body whorl; 8 ribs on the penultimate whorl, 7 on the body whorl to the varix. Strong growth striae are present that run obliquely over the ribs, are arcuate on the whorl’s shoulder. Varix larger than adjoining ribs, about twice the width, positioned about ⅓-turn from edge of outer lip. Spiral sculpture of closely packed, very fine microscopic grooves or threads, intersected by microscopic growth striae, the pattern of which is mostly worn off on the holotype but distinct on the paratypes. Sulcus indistinct, only the reduced, slightly recurved ribs and striae on the shoulder mark the prior positions of the anal sinus. Outer lip thin, flattened, with 2 strengthening axial folds; edge of lip forms a low arc from the anal sinus to the stromboid notch. Stromboid notch shallow. Anal sinus deep, with a rounded apex, and a flared inner edge; parietal callus causing it to be laterally directed. Inner lip margined, detached anteriorly, thin on the parietal wall, forming a low callus posteriorly, at the anal sinus; edge of lip shows layers from multiple depositions. Anterior canal short but well defined, open, deep and turned to the right when viewed ventrally; unnotched. Anterior fasciole slightly swollen, with 6 spiral ridges. Color creamy white with 2 bands of dark reddish-brown, one on shoulder broken by ribs, second below the shell’s periphery, not broken by the ribs, and visible only on the body whorl.

Remarks. Taxonomy. Decoradrillia interstincta has all the characteristics of Decoradrillia , including ribs that extend from suture-to-suture, a narrow varix, and short but well defined anterior canal. Variability. The three specimens in the type series have an average total length of 11.3 mm (10.7–12.0 mm), and average W/ L ratio of 0.366. Color appears to vary principally in intensity and extent of the dark reddish-brown color between the axials. Identification. D. interstincta is most similar to D. harlequina , new species, in that it has similar interrupted bands of brown color. It differs in being smaller, and in lacking the widely spaced heavier spiral threads on the last whorl.

Etymology. The Spotted Decoradrillia . Named for the spotted appearance of the shell due to the darker color of the spiral bands in intercostal spaces.

Figures

PLATE 51. Decoradrillia spp. shell surface SEM images. Figs. 1 – 2: Decoradrillia pulchella (Reeve, 1845), Anse Bateau Bay, Tobago I., Trinidad & Tobago (ANSP 338495), 240 x & 930 x, respectively. Figs. 3 – 4: Decoradrillia harlequina, new species: Fig. 3: Indian Cay, Grand Bahama I. (ANSP 366927), 240 x; Fig. 4: holotype, Devil’s Bay, Grenada (USNM 1291335), 1,000 x. Figs. 5 – 6: Decoradrillia interstincta, new species, " Big Rocks ", Utila I., Bay Is., Honduras (ANSP 464986), 250 x & 1,000 x, respectively.