Caecum orcutti Dall in Orcutt, 1885

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 104-105

Caecum orcutti Dall in Orcutt, 1885

Figures 81 A–F, 82A–K, 83A–B, 126I

Caecum orcutti Dall in Orcutt, 1885: 541 , holotype USNM 60927 , San Diego , California.

Caecum (Fartulum) orcutti —Abbott, 1974: 93, fig. 890.

Fartulum orcutti — McLean, 1978: 30, fig. 14.4.

Caecum orcutti — Raines, 2019: 101, figs. 3A–B.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1964 - 32.39 , N of Ensenada , Baja California, Mexico, intertidal, 200+ sh ; LACM 1967 - 2.57 , San Tomas Point , Baja California, Mexico, intertidal, 20 sh ; LACM 1972 - 205.18 , Paradise Cove , Los Angeles Co., California, 0–5 m, 6 sh ; LACM 1966 - 1.46 , S of San Tomas Point , Baja California, Mexico, intertidal to 7 m, 50 sh . SBMNH: SBMNH 621663 , Prisoners Harbor , W of Santa Barbara County, California, USA, intertidal, 1 sh ; SBMNH 214951 , Piedras Blancas , San Luis Obispo County, California, USA, 35 sh ; SBMNH 619735 , Reef Point , Orange County, California, USA, 12 sh ; SBMNH 214949 , San Pedro , Los Angeles County, California, USA, 50 sh ; SBMNH 6938 , Rocky Point , Santa Barbara County, California, USA, 3 sh ; SBMNH 6903 , Malaga Cove , Los Angeles County, California, USA, 9 sh ; SBMNH 120454 , Cayucos , San Luis Obispo County, California, USA, 18 sh ; SBMNH 114639 , Bahia Todos Santos , Baja California [Norte], Mexico, 1 sh ; SBMNH 120504 , Point Fermin , Los Angeles County, California, USA, 10 sh ; SBMNH 619736 , Palos Verdes , Los Angeles County, California, USA, 50 sh ; SBMNH 455 , Portuguese Bend , Los Angeles County, California, USA, 15 sh ; SBMNH 110421 , Point Pines , Monterey County, California, USA, 1 sh ; SBMNH 33319 , San Pedro , Los Angeles County, California, USA, 13 sh .

Original diagnosis. “Shell small, stout, smooth, but not polished, light warm brown in color and without sculpture, except very slight lines of growth. Shell slightly curved, the anterior aperture very oblique, about at right angles to the plane of the diameter of the plug, the superior margin being the anterior; plug glandiform, smooth, rounded without mucro; operculum brown, thin, smooth.” Dall in Orcutt (1885: 541).

Description. Protoconch multispiral (about 1.85 whorls), planispiral, smooth ( Fig. 82A ), transition to teleoconch I marked by apertural varix ( Fig. 82A ). Teleoconch I short, smooth ( Fig. 82B ), transition to teleoconch II marked by slight incised axial line ( Figs. 82A , D–E). Teleoconch II about 2.5 times length of teleoconch I, sculptured with very weak axial growth marks ( Fig. 82C ), transition to teleoconch III marked by slight incised axial line ( Fig. 82E ). Teleoconch III sculptured with numerous axial growth marks ( Fig. 82I ), transition to teleoconch IV marked by incised axial line or constriction ( Fig. 82E ). Teleoconch IV with identical characters as previous stage, transition to teleoconch V marked by suture ( Fig. 82G ). Teleoconch V surface smooth with very fine growth lines ( Figs. 82H, J ), transition to teleoconch VI marked by suture ( Fig. 83A ). Teleoconch VI (last growth stage) average size for genus [Tol 2.00– 2.20 mm], larger than previous stage, tubular, stout, mildly and regularly arched [Larc: 0.59–0.60 mm; Arc: 0.11–0.15 mm] ( Fig. 82J ), with slight increase in diameter from posterior to aperture, semitranslucent white to tan ( Fig. 81B ). Surface smooth with very fine growth lines ( Fig. 82J ). Posterior [Dpe: 0.45–0.47 mm] with rounded to squared shoulder ( Fig. 81C ). Septum hemispherical, pronounced ( Fig. 81C ). Mucro low, heel-like, positioned on dorsal margin, usually covered by septum ( Fig. 81C ). Aperture [Da: 0.50–0.54 mm] oblique ( Fig. 82K ). No varix. Lip smooth ( Fig. 81C ). Periostracum thin, smooth, reddish brown ( Fig. 81A ). Operculum thin, brown; exterior surface with 10–11 fine concentric rings ( Figs. 81 D–E). Conceptual reconstruction of growth stages shown in Fig. 83A .

Distribution and Habitat. From Pacific Grove, Monterey County, California to Asuncion Island, Baja California. Intertidal to 7 m. Abundant on protected rocky substrates.

Remarks. The holotype of Caecum orcutti is an adult specimen (USNM 60927, Fig. 81F ). The degree of aperture obliqueness is variable within C. orcutti , making it sometimes difficult to tell the difference between a late subadult stage and a mature specimen.

Figures

FIGURE 81. Caecum orcutti. A. Profile view with periostracum (LACM 1964-32.39). B. Profile view without periostracum (LACM 1964-32.39). C. Ventral view (LACM 1972-205.18). D. Operculum, exterior surface (SBMNH 33319). E. Operculum, interior surface (SBMNH 33319). F. Holotype, USNM 60927.

FIGURE 82. Caecum orcutti shells at different growth stages. A. Protoconch and teleoconchs I to II (LACM 1964-32.39). B. Surface of teleoconch I (LACM 1964-32.39). C. Surface of teleoconch II (LACM 1964-32.39). D. Teleoconchs I to II (LACM 1964-32.39). E. Teleoconchs I to III (SBMNH 33319). F. Teleoconch IV (SBMNH 33319). G. Teleoconchs IV to V (SBMNH 33319). H. Teleoconch V (SBMNH 33319). I. Surface of teleoconchs III to IV (SBMNH 33319). J. Surface of teleoconchs V to VI (SBMNH 33319). K. Teleoconch VI (SBMNH 33319).

FIGURE 83. Caecum orcutti. A. Conceptual reconstruction of growth stages. B. Species distribution map.