Caecum teres Carpenter, 1857

Figures 51 A–J, 52A–E, 53A–B, 126O

Caecum (Fartulum) teres Carpenter, 1857: 329, syntype NHMUK 1857.6.4.1550, Mazatlan .

Caecum (Fartulum) teres — Carpenter, 1859: 434.

Caecum teres — Carpenter, 1860: 33; Palmer, 1951: 44; Brann, 1966: pl. 37, fig. 378; Pizzini et al. 2007: 6, figs. 3g–h. Fartulum teres — Keen, 1968: 420, fig. 94; Keen, 1971: 398; Kaiser, 1997: 29; Finet et al. 2016: 96.

Brochina teres — Lightfoot, 1993b: 78, fig. 24.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1934 - 271.11, Sulivan Bay, James Island, Galapagos Islands, 37 m, 2 sh ; LACM 1938 - 219.3, Sechura Bay, Piura Dept., Peru, 17 m, 1 sh ; LACM 1974 - 7.3, Islas Lobos de Afuera, Lambayeque Dept., Peru, 45 m, 5 sh ; LACM 1965 - 21.69, Otoque Island, Panama Bay, Panama Prov., Panama, 9–27 m, 2 sh ; LACM 1933 - 154.3, Chatham Bay, Cocos Island, Costa Rica, 32 m, 1 sh ; LACM 1972 - 45.44, Ballena Bay, Puntarenas Prov., Costa Rica, 5–18 m, 1 sh ; LACM 1935 - 111.16, Port Parker, Guanacaste Prov., Costa Rica, 9 m, 1 sh ; LACM 1972 - 53.36, Herradura Bay, Puntarenas Prov., Costa Rica, 22 m, 4 sh ; LACM 1973 - 57.10, Zacatillo Island, La Union Prov., El Salvador, 2 m, 20 sh ; LACM 1933 - 136.2, Petatlan, Guerrero, Mexico, 11 m, 15 sh ; LACM 1968 - 45.56, Cuastecomate Bay, Jalisco, Mexico, 18–37 m, 4 sh ; LACM 1967 - 15.18, Banderas Bay, Jalisco, Mexico, 5–11 m, 12 sh ; LACM 1971 - 83.58, Los Arcos, Banderas Bay, Jalisco, Mexico, intertidal to 3 m, 2 sh ; LACM 1965 - 13.46, Maria Cleofas Island, Tres Marias Islands, Nayarit, Mexico, intertidal to 3 m, 1 sh ; LACM 1960 - 20.13, 40 miles S of Mazatlan, Sinaloa, Mexico, 32–37 m, 4 sh ; LACM 1960 - 19.6, Mazatlan, Sinaloa, Mexico, 37 m, 3 sh ; LACM 1968 - 14.30, Estero Soldado, NW of Guaymas, Sonora, Mexico, intertidal, 1 sh ; LACM 1973 - 5.50, Estero Soldado, NW of Guaymas, Sonora, Mexico, intertidal, 2 sh ; LACM 1936 - 181.3, San Pedro Nolasco Island, Sonora, Mexico, 22 m, 2 sh ; LACM 1961 - 2.11, San Carlos Bay, Guaymas, Sonora, Mexico, intertidal, 2 sh ; LACM 1934 - 257.1, Braithwaite Bay, Socorro Island, Mexico, 24 m, 1 sh ; LACM 1963 - 257.11, El Tule, Canelo Bay, Baja California, Mexico, 18 m, 1 sh ; LACM 1941 - 352.3, NW of Natividad Island, Baja California Sur, Mexico, 55 m, 1 sh ; LACM 1969 - 25.22, Willard Island, San Luis Gonzaga Bay, Baja California, Mexico, 18–27 m 10 sh ; LACM 1967 - 70.30, Magdalena Island, Magdalena Bay, Baja California Sur, Mexico, 2–10 m, 11 sh ; LACM 1973 - 95.5, Los Cobanos, Sonsonate Dept., El Salvador, 2 m, 1 sh ; LACM 1965 - 14.34, Maria Cleofas Island, Tres Marietas Islands, Mexico, 2–10 m, 2 sh . SBMNH: SBMNH 620470, Estero Morua, Sonora, Mexico, intertidal, 50 sh ; SBMNH 621320, Estero Morua, Sonora, Mexico, intertidal, 5 sh; SBMNH 126599, Punta Camaron, Mazatlan, Sinaloa, Mexico, intertidal, 3 sh ; SBMNH 127139, Chacala, Nayarit, Mexico, 3–5 m, 3 sh; SBMNH 620607, Bahia La Choya, Sonora, Mexico, intertidal, 1 sh ; SBMNH 129977, Puertecitos, 1.5 mi N [Playa Curbina], Baja California [ Norte], Mexico, intertidal, 1 sh ; SBMNH 118497, Punta San Felipe, San Felipe, Baja California [Norte], Mexico, intertidal, 20 sh ; SBMNH 619851, Ensenada Blanca [N of San Felipe], San Felipe, Baja California [Norte], Mexico, intertidal, 20 sh ; SBMNH 619906, Balboa, Panama Prov., Panama, 3 sh ; SBMNH 620166, Puerto Penasco, Sonora, Mexico, 3 sh ; SBMNH 620465, Bahia San Carlos, San Carlos Nuevo Guaymas, Sonora, Mexico, 15–30 m, 5 sh ; SBMNH 620466, Bahia La Choya, Sonora, Mexico, 6–16 m, 1 sh ; SBMNH 620467, Tisate, Bahia Banderas, Jalisco, Mexico, intertidal, 1 sh ; SBMNH 620468, Santa Cruz, Nayarit, Mexico, intertidal, 3 sh; SBMNH 620469, Puerto San Carlos, Bahia Magdalena, Baja California Sur, Mexico, 2–10 m, 30 sh ; SBMNH 131816, Santa Clara, Sonora, Mexico, intertidal, 1 sh; SBMNH 114041, Isla Natividad, opposite Flat Rock, Baja California Sur, Mexico, intertidal, 1 sh; SBMNH 621630, Islas Dos Amigos [N islet], Puntarenas, Costa Rica, 10–30 m, 1 sh ; SBMNH 622516, Estero Morua, Sonora, Mexico, intertidal, 1 sh. BCD: Navidad Bar, Colima, Mexico, 16–32 m, 30 sh .

Original diagnosis. “ C. ( Fartulum) t. elongata, arcuata, tereti, laevi; longitudinaliter interdum obsolete subangulata; albida, seu huc et illuc semicornea; apertura parum constricta, dein minime reflexa, parum declivi; septo mucronato; mucronem versus parum ascendente margine subrecto; mucrone ad frontem subelongata, ad latus angusta, parva, obtusa: operculo vix concavo.” Carpenter (1857: 329).

Description. Protoconch and teleoconch I unknown. Teleoconch II short, smooth (Fig. 52B), transition to teleoconch III marked by weak, incised axial line (Fig. 52A). Teleoconch III about 2.5 times length of teleoconch II, smooth or sculptured with numerous, weak longitudinal striae (Figs. 52 B–C), transition to teleoconch IV marked by slight axial constriction (Fig. 52A). Teleoconch IV with identical characters as previous stage, mucro pronounced, heel-shaped, positioned along dorsal margin (Fig. 52D), transition to teleoconch V marked by axial constriction (Fig. 52D). Teleoconch V (last growth stage) average size for genus [Tol 1.85–3.10 mm], tubular, rather thick, mildly and regularly arched [Larc: 0.63–0.88 mm; Arc: 0.09–0.10 mm], subcylindrical with increase in diameter from posterior to aperture, semi-translucent white (Figs. 52 A–B). Surface smooth or sculptured with numerous, weak longitudinal striae (Figs. 52 B–C). Posterior [Dpe: 0.18–0.19 mm] with thin edge, rounded shoulder (Fig. 51C). Septum mucronate, pronounced (Fig. 51C). Mucro low rounded, heel-shaped, positioned on dorsal margin (Fig. 51C). Aperture [Da: 0.48–0.51 mm] simple (Fig. 52E). No varix. Lip smooth (Fig. 51C). Periostracum thin, textured, yellowish (Figs. 51A, G–H). Operculum thin, light brown; exterior surface with 6–8 concentric rings (Figs. 51 D–E). Conceptual reconstruction of growth stages shown in Fig. 53A.

Distribution and Habitat. From Magdalena Bay, Baja California, Mexico to Sechura Bay, Peru, including the Gulf of California, the Revillagigedo Islands, Cocos Island, and the Galapagos Islands. Intertidal to 55 m. Common on sand and rubble substrates.

Remarks. The largest specimen from the type material of Caecum teres is a late subadult (NHMUK 1857.6.4.1550, Fig. 51F). The surface of C. teres may appear smooth or display microsculpture consisting of short, longitudinal striae (Figs. 51 I–J). However, the periostracum always has well-defined microsculpture (Figs. 51 G–H). Adult C. teres and C. corrugulatum have similar shaped teleoconchs. However, their growth morphologies and microsculpture are quite different.