Sternaspis maior Chamberlin 1919

Neotype (UNAM 7882), with body browinish, paler without the papillar layer (Fig. 11A, B). Introvert expanded, markedly wider than abdomen, covered with abundant small papillae. Abdomen with abundant, homogeneously distributed papillae. Body 17 mm long, 6 mm wide (complete paraneotypes 19.5–20.0 mm long, 7–10 mm wide), about 29 segments. Prostomium hemispherical, paler than surrounding areas (Fig. 11C). Peristomium round, without papillae. Mouth oval, covered by papillae, restricted to a circular region around the mouth. First three chaetigers with 12–14 golden, widely separated, falcate introvert hooks per bundle, each with subdistal dark areas (Fig. 11B, C). Genital papillae lost, eroded from the intersegmental groove between segments 7 and 8. Pre-shield region with 7 segments, with papillae abundant, evenly distributed. No capillary chaetae seen. Ventro-caudal shield with ribs, but no concentric lines; suture restricted to anterior region. Anterior margins rounded; anterior depression shallow; anterior keels not exposed (Fig. 11A, D). Lateral margins gently rounded, expanded posteriorly. Fan truncate, not extended beyond posterior shield corners, with a median notch, crenulated. Marginal chaetal fascicles include 10 lateral ones (Fig. 11B, D), chaetae ovally arranged and 8 posterior fascicles, chaetae in linear arrangement. Peg chaetae on conical extensions emerging under shield corners. Peg chaetae with stout base in cross section; a small fascicle of delicate capillary chaetae (peg-associated capillary chaetae) between peg chaetae and first fascicle of posterior chaetae. Branchiae numerous, thick, coiled, slender, long, protruding from two oval plates, separated by a wide angle, on either side of the anus. Additional fine, long filamentous papillae extending along the posterior margin of the shield.

Central part of the Gulf of California, México, in soft bottoms at 180–965 m, but the original material was collected at 1143 m.