Cerithium amirantium E. A. Smith 1884

Cerithium amirantium E.A. Smith, 1884

Cerithium amirantium E.A. Smith, 1884:501, pl. 44: fig. R [lectotype, herein selected: BMNH 1882126221; type locality: Darros Id, Amirantes, Seychelles, 4 m; 14 × 4.4 mm].

DESCRIPTION.—Shell (Figure 13): Shell small, turreted, reaching 13.7 mm in length, and comprising about 12 inflated, somewhat angulate whorls. Protoconch unknown. Early whorls with 3 spiral cords and strong axial ribs, Teleoconch whorls each with strong varix; largest varix on body whorl opposite outer lip of aperture. Posterior of each whorl broadly beveled at suture, especially on early whorls, Teleoconch whorls sculptured with 4 major beaded, spiral cords and 5 thin spiral lirae. Anterior 2 spiral cords dominant, but subsutural cord sometimes well developed. Fifteen to 20 axial ribs present on each whorl, most prominent on middle whorls. Spiral cords form beads at intersections with axial ribs. Body whorl sculptured with six major spiral cords and many fine spiral lirae. Subsutural cord and two cords adjacent to siphonal constriction well developed and with prominent beads. Base of body whorl concave, sculptured with fine spiral lirae. Aperture ovate, a little less than one-fourth the shell length. Columella concave. Siphonal canal short, slightly turned to left, about 45° to shell axis. Shell somewhat vitreous, pink to white with white varices and subsutural band or dots of light brown. Columella light purple. Measurements (Table 10). Operculum unknown.

Radula: Unknown.

Anatomy: Unknown.

DISTRIBUTION.—Present records indicate this species is endemic to the Amirantes, Seychelles, and Mauritius islands.

SPECIMENS EXAMINED.—INDIAN OCEAN ISLANDS: 500–600 m, 11°28'5″S, 47°12'5″E, Benthedi sta DR-6, Îles Glorieuses (MNHNP); 440 m, 11°28'5″S, 47°17'7″E, Benthedi sta DS-10, W of Îles Glorieuses (MNHNP); 21°21'S, 65°52'E, Rodriguez Id, off Mauritius (USNM 716636).

Cerithium atromarginatum Dautzenberg and Bouge, 1933

Cerithium maculosum Mighels, 1845:22 [type not found; type locality: Oahu; not Cerithium maculosum Kiener, 1841].—Sowerby, 1865, pl. 14: fig. 97.—Tryon, 1887:137, pl. 26: figs. 75, 76.—Kobelt, 1898:216, pl. 38: figs. 10, 11.

Cerithium nassoides Sowerby, 1855:875, pl. 183: figs. 200. 201 [lectotype, largest of 2 syntypes herein selected: BMNH 1964411; type locality: Sandwich Islands; 14.4 mm × 6.7 mm; not Cerithium nassoides Grateloupe, 1832]; 1865, pl. 12: fig. 83.—Tryon, 1887:137, pl. 26: fig. 76.—Kobelt, 1898:216. pl. 38: figs. 10, 11.—Couturier, 1907:155.

Cerithium nassaide var. minor Couturier, 1907:155 [holotype: MNHNP, no number, type locality: Rikilea; Makapon; not C. minor C. Moore, 1866].

Cerithium atromarginatum Dautzenberg and Bouge (ex Vignal), 1933:304–305 [new name for C. maculosum Mighels, 1845, and C. nassoides Sowerby, 1855. both preoccupied].—Lamy, 1938:137.—Steele, 1957:112.—Tinker. 1958:36. figs.—Kay. 1979:121, fig. 45F.

Cerithium (Conocerithium) atromarginatum Dautzenberg and Bouge.—Maes, 1967:113. pl. 6: fig. L.

Cerithium bavayi Vignal.—Cemohorsky, 1972:69, pl. 15: fig. 9 [in part, left-hand figure only].

Cerithium (Conocerithium) aff. C. egenum Gould.—Ladd, 1972:40, pl. 9: fig. 11.

Cerithium (Thericium) atromarginatum Dautzenberg and Bouge.—Render, 1980:36–37.

DESCRIPTION.—Shell (Figure 14): Shell small, stocky, conical-acute, with broad base, reaching 15.5 mm length, 6 mm width, and comprising 8–10 inflated, angulately nodose whorls. Protoconch I (Figure 14I) smooth, 1.5 whorls; protoconch II (Figure 14I) 3.5 whorls, sculptured with two spiral cords and subsutural plications. Microscopic, prosocline axial striae between spiral cords, becoming opisthocline presuturally. Early teleoconch whorls sculptured with fine spiral striae (Figure 14F). Teleoconch whorls weakly sculptured with 11–13 smooth, crowded, spiral cords; sometimes without sculpture. Dominant spiral cord in middle of each whorl. Spiral cords crossed with many subsutural axial plaits and by broad axial ribs extending anteriorly from mid-whorl. Body whorl large, broad, sculptured similar to other teleoconch whorls, but having numerous, fine spiral striae and a few spiral cords on shell base. Base of body whorl slightly constricted at anterior siphon. Varix opposite outer lip of aperture. Aperture ovate, large, a little more than one-third the shell length. Columella concave with slight callus. Anterior canal short, well defined. Anal canal defined by parietal columellar plait extending well into shell aperture. Outer lip convex, smooth, slightly thickened at edge and with very small denticles at interior edge. Shell color white with variable brown spots, dots and blotches. Large, reddish brown blotch at posterior end of outer lip; anterior part of outer lip frequently reddish brown. Brown axial flammules or blotches consistently between subsutural plaits and small spiral dots or dashes occasionally on spiral cords. Some shells nearly melanistic (Figure 14D). Measurements (Table 11). Periostracum thin, tan. Operculum corneous, thin, light tan, nearly transparent, paucispiral, with eccentric nucleus.

Radula (Figure 15): Type-1 radular ribbon (Figure 3A). Rachidian tooth (Figure 15B,C) squarish, anteriorly convex, with slight concave central depression. Basal plate with basal-lateral, lunule-shaped ridge on each side and with central, posterior extension. Cutting edge with spade-shaped main cusp flanked on each side with two small denticles. Lateral tooth (Figure 15B,C) trapezoid, having basal plate with large, posteriorly extending central ridge, notched inner edge, and long, lateral, posterior extension. Central ridge bears small, blunt denticle. Cutting edge of lateral tooth with long, pointed main cusp, single inner flanking denticle, and 3 or 4 outer, flanking denticles. Marginal teeth (Figure 15B,C) with long, thin shafts, broad, spatulate bases, and curved apices with long, pointed main cusps at tips. Inner marginal tooth with three inner pointed, flanking denticles and three outer-flanking denticles. Outer marginal tooth same, but without outer flanking denticles.

Anatomy: Animal flesh color, flecked with yellow, white, and tan. Sides of foot, head, snout, and tentacles pink; very small red dots on snout and tentacle tips. Anterior sole with deep propodial groove. Females with wide, ciliated groove emerging from distal palliai oviduct and terminating in lateral glandular pit (ovipositor) on right side of foot Snout highly extensible. Dorsal and lateral mantle edge with white papillae, mantle roof green.

Type-A palliai oviduct configuration (Figure 4A). Albumen gland thick, white; distal, white capsule gland. Sperm gutter with large opening in anterior medial lamina, becoming narrow tube in medial lamina edge, enlarging posteriorly to form large, spermatophore bursa. Small, lobate seminal receptacle in outer wall of proximal medial lamina adjacent to spermatophore bursa. No connection between bursa and seminal receptacle observed. Seminal receptacle of medial lamina directly across from seminal receptacle of lateral lamina. Lateral lamina of palliai oviduct thin, with distal opening into long, thin tube leading to proximal seminal receptacle.

Pair of small, glandular salivary glands lying behind nerve ring, each becoming simple tube passing through nerve ring and opening into dorsal-lateral buccal cavity.

SYNONYMIC