Ammonicera mcleani sp. nov.

Figure 5

Examined material (19 specimens). Holotype: LACM 3284 (SEM, color photograph before SEM), W side of Cerralvo Is., Baja California, Mexico, 24°10’N, 109°52’W, 30–50 ft [9.1–15.2m], leg. James H. McLean, 3 February 1971 . Paratypes (3): LACM 3285 (Paratypes 1, 2; SEM), from the holotype lot; FMNH 339461 (Paratype 3, SEM), from the holotype lot. Additional material: LACM 71-24, 11 specimens from the type locality; LACM 71-14, 3 specimens, east side of Punta Entrada at Sail Rock (north entrance to Magdalena Bay), Baja California, Mexico (24°32.4’N, 112°04’W, 10–50 ft [3–15.2m], leg. James H. McLean, 30-31 January 1971; LACM 71–177, 1 specimen, Punta San Pablo anchorage, outer coast of Baja California, Mexico (27°12’55”N, 114°27’30”W, 70–80 ft [21.3–24.4m], leg. Swift & Huddleston, 24 October 1971.

Diagnosis. Ammonicera with spiral cords delimiting a broadly convex peripheral wall; additionally sculptured by a single row of 19–21 nodules each on the apical and basal walls of the body whorl.

Description. Shell planispiral, tightly coiled. Shell wall very thin, pellucid, glossy, amber in coloration (faded specimens with major cords darkest). Protoconch of c. 1.3 whorls, sculptured on its apical and basal surfaces by 3 spiral cords; central spiral cord positioned mid-whorl, broad, prominent, with a reticulate sculpture on its outer face; inner and outer spiral cords positioned approximately equidistantly between the central cord and the inner and outer sutures, respectively, c. 1/4 the width and height of the central cord. Protoconch 2 stage absent; boundary between protoconch and teleoconch poorly marked. Teleoconch of c. 1.4 whorls, sculptured by 1 broad spiral cord each at the junction of the peripheral wall with the apical and basal walls, and by 1 spiral row of axially elongated nodules, positioned mid-whorl, with interspaces c. 1–2 times their width, gradually increasing in height throughout the teleoconch; body whorl with 19–21 nodules on each row; secondary sculpture of the teleoconch composed of very fine and somewhat wavy spiral grooves. Shell periphery broadly convex. Apical and umbilical sutures shallowly impressed; outer lip straight to broadly convex from the sutures to the middle of the apical and basal walls, and from these points to the junctions with the peripheral wall, broadly convex along the shell periphery; outer lip forming 4 similar, obtuse vertices in the middle of the apical and basal walls, and at the junctions of these walls with the peripheral wall; inner lip concave, not flaring. Aperture almost hexagonal.

Shell dimensions (in mm) and whorl counts:

Remarks. The shells of Ammonicera mcleani and A. mexicana sp. nov. (described below) resemble those of Atlantic A. sculpturata Rolán, 1992b and Papua New Guinean A. nodicarinata (Sleurs, 1985c) in the presence of two spiral cords delimiting the peripheral wall and a single row of nodules on the apical and basal surfaces of the shell. They differ from both of these previously described species in bearing smaller and more numerous nodules on the body whorl (10–15 in A. nodicarinata; c. 12 in A. sculpturata). They additionally differ from A. sculpturata in having a less rounded aperture, and from A. nodicarinata in the later ontogenetic onset of their nodules (see Rolán, 1992b; Sleurs, 1985c).

The shape of the periphery is the most obvious criterion to distinguish A. mcleani and A. mexicana . It is broadly convex in the former species, whereas in the latter a prominent spiral cord divides the peripheral wall in two concave sectors. Additional distinguishing features are the more discoidal shape of A. mexicana and the slightly more prominent nodules of A. mcleani .

Etymology. This species is dedicated to Dr. James McLean, Curator Emeritus at LACM and renowned specialist of the eastern Pacific gastropod fauna, who personally collected and encouraged us to study the material reported upon in this paper.