Chlamys hanaishiensis hanaishiensis Masuda, 1962
MASUDA, K. 1962. Tertiary Pectinidae of Japan. Science Reports of the Tohoku University [2nd. Series - Geology], 33 (2): 117-238, pls. 18-27.
[p. 166, pl. 22, figs. 1, 2]
1962 Chlamys hanaishiensis Masuda, 1962
K. Masuda, 1962, plate 22.
|
«Pecten islandicus MülIer, Yoshiwara, 1902, p. 144, pI. 2, figs. 5a-b (?) (non Müller, 1776).
Chlamys erythrocomata (Dall), Kinoshita and Isahaya, 1934, p. 14, pI. 11, fig. 75 (non DalI, 1907). Chlamys islandica (Mueller,) Kubota, 1950c, p. 96, pI. 8, fig. 53 (non MiilIer, 1776). Chlamys (Chlamys) islandica erythrocomata (Dall), Habe, 1951, p. 73, figs. 140, 141 (non Dall, 1907). Chlamys islandica erythrocomata (Dall), Kira, 1955, p. 99, pI. 49, fig. 13; Oyama, 1959, 2, figs. 4, 5 (non Dall, 1907). Holotype: — DGS, Reg. No. 3935. Description: — Shell moderate in thickness and convexity, higher than long, suborbicular, nearly equivalve; valves radiately ribbed, apical angle about 90°. Right valve with about 28, distinct, roundly flat-topped, finely scaled radial ribs, finely scaled intercalary threads, concentric growth lines and obtuse network; radial ribs somewnat broader than their interspaces, subequal or sometimes unequal to each other in strength, usually smooth on upper part of disc but tend to become imbricated towards ventral margin, usually divide into two, subequal riblets by a shallow longitudinal furrow near ventral margin, or sometimes remain undivided; interspaces between radial ribs round-bottomed, sometimes irregular in breadth, usually with obtuse network; submargins sculptured with subordinate, finely scaled, fine radial threads; primary intercalary threads usually appear on upper part of disc, narrower than divided riblets in strength at ventral margin; secondary ones appear on lower part of disc; auricles moderate in size; anterior larger than posterior, with conspicuous byssal notch and moderate byssal area, and several, finely scaled radial threads and distinct fine concentric lines; posterior one truncated behind at obtuse angle, with finely scaled radial threads narrower and more numerous than those of anterior, finely scaled intercalary threads and concentric lines; hinge with simple cardinal crura, and deep resilial pit with low and short, straight, fine lateral ridges and conspicuous ctenolium. Left valve with elevated, flatly round-topped, finely imbricated radial ribs, finely scaled intercalary threads, concentric growth lines and obtuse network; radial ribs narrower than their interspaces, sometimes unequal to each other in strength corresponding to sculpture of right valve, usually divide into two or three or rarely more riblets towards ventral margin, but in case of less prominent radials subequal in strength and usually remain undivided; submargins sculptured with subordinate, finely scaled, faint, fine radial threads; interspaces between radial ribs with obtuse network, with a single or sometimes two, finely scaled, fine intercalary threads; primary intercalary threads usually appear on about half of disc and secondary ones near ventral margin; anterior auricle larger than posterior, sculptured with several, finely scaled radial threads, intercalary threads and concentric lines; posterior similar to anterior in sculpture. Interior surface gently folded corresponding to external sculpture, and with fine marginal serration. Dimensions (in mm.): --
Comparison and Affinity: — The present species is related to Chlamys islandica (Müller) (Op. cit.), but differs by its fewer radial ribs which are more prominent, finely scaled and somewhat unequal in strength and rather prominent intercalary threads. From Chlamys cosibensis group it differs by its larger shell, greater number of radial ribs and less distinct concentric constrictions.
Remarks: — Kubota (1950c) stated that since Kinoshita and Isahaya's erythrocomata (1934) has rather broad ribs which do not make fascicular bundles, it may be distinct from Dall's species, and for it he suggested the name var. kinoshitai. However, he did not make an actual proposal, and did not describe his new variety but stated that it is similar to his var. osugii but is larger and that the ribs do not make fascicles. He did not figure his kinoshitai. Thus it is evident that Kubota merely suspected Kinoshita and Isahaya's identification of their specimen with Dall's erythrocomata, found a specimen identifiable with their erythrocomata and suggested a new name for it but without description or figure and compared it with his newly proposed variety osugii. From this procedure it may be judged that since neither description nor figures accompanied his suggestion for a new name for Kinoshita and Isahaya's erythrocomata, the varietal name kinoshitai is not valid. Type locality, Geological formation and Age: — Left floor of the Toshibetsu River, about 1 km. southwest of Pirika station of the Setana Line, Imagane-machi, Setana-gun, Shiribeshi Province, Hokkaido (Lat. 42°27'28"N., Long. 141°11'37"E.). Setana formation. Early Pliocene. Distribution: — Setana formation, Hokkaido; Northern Pacific, Bering Sea and Okhotsk Sea: Early Pliocene to Recent. Occurrence: — Common in the medium-grained sandstone.» KÔICHIRÔ MASUDA, 1962
|