Pycnolepas aff. rigida (J. de C. Sowerby, 1836)

(Fig. 3)

Localities and horizon. Localities 901 and 1024-I, near Vassa (Vassinskaja protoka), southwest of Bogorodskoye, Khabarovsk region (Fig. 2); middle Albian (Sey et al., 2004: table 6), zone of Cleoniceras sp. and Inoceramus ex gr. anglicus Woods, 1911 . Associated faunal elements include the inoceramid bivalve I. udylensis Zonova, 1989 and ammonoids ( Beudanticeras sp., Marshallites sp.).

Material. Three right scuta (VSEGEI/ CNIGR Museum, nos 57/13062, 58/13062, 130/13062), one left scutum (VSEGEI/ CNIGR Museum, no. 128/13062) and a single, fragmentary carina (VSEGEI/ CNIGR Museum, no. 129/13062), collected in 1966 and 2000 by V.D. Ovchinnikov and L.P. Ejkhvald, respectively.

Description. Scuta are elongately triangular, strongly convex transversely, mainly in apical portion; apex strongly curved towards terga; basilateral portion slightly produced; occludent margin strongly convex; basal margin near-straight, oblique; upper part of tergo-lateral margin concave, lower part rounded, protuberant; apicobasal ridge conspicuous, of variable width, extending from apex to basilateral angle, with perpendicular sides and marked with transverse ridges of highly variable prominence; ornament on occludent and tergo-lateral sides of apicobasal ridge consisting of close-set transverse ridges, variable in number and spacing; no longitudinal ridges seen, but this may be preservation induced; inner side not exposed.

As preserved, VSEGEI/CNIGR Museum, no. 130/13062 (Fig. 3 D), not illustrated by Sey et al. (2004), is c. 20 mm in length; maximum width (basal margin) is 9.5 mm, apicobasal ridge c. 2 mm at its widest point; ornament strongly abraded. VSEGEI/CNIGR Museum, no. 57/13062 (Fig. 3 B) measures 15 mm in length, and 9 mm in width; basitergal angle broken; apparently damaged after publication by Sey et al. (2004) and glued; apicobasal ridge flattened, conspicuously wide, with prominent sides. VSEGEI/CNIGR Museum, no. 58/13062 (Fig. 3 A) also has suffered extensive damage since it was illustrated by Sey et al. (2004: pl. 92, fig. 15a, b), the occludent portion is now missing; as preserved, it measures 13 mm in length and c. 10.5 mm in width, showing an abraded apicobasal ridge. VSEGEI/CNIGR Museum, no. 128/13062 (Fig. 3 C) is the best preserved valve in the present lot; it measures 22 mm in length and c. 10 mm in width; apicobasal ridge well developed, 1 mm in width and divided into two by a shallow central furrow.

The carina (VSEGEI/CNIGR Museum, no. 129/13062; Fig. 3 E, not illustrated by Sey et al., 2004) is broken apically and basally; semicylindrical, moderately curved inwards, strongly convex transversely, yet not carinate, basal margin slightly concave centrally; ornament of irregularly spaced, raised and slightly undulating ridges; interspaces (near-) smooth. As preserved, it measures 15 mm in length (estimated to have been> 20 mm originally), with basal width of at least 6.5 mm.

No other capitular valves or imbricating plates known.