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The pelecypod genera Otapirta Marwick and Lupherella Imlay, n. gen., both resembling the late Triassic genus Monotis, are recorded for the first 1time from Mesozoic bed•s in the United States. Lupllerella is represented by L. boechiformis (Hyatt) from beds of Pliensbachi·an age in eastern Oregon and California. It has not been found elsewhere. One species of Otapiri.a, named 0. tailleuri Imlay, n. sp., has been found in northern Alaska associated with or directly underlying Inoceramus cf. I. lucifer Eichwald, whose presence indicates an early Middle Jurassic or late IDarly Jurassic age not older than Toarcian. Another species, ·referred to as 0. sp. undet., has been found as float in the upper Yukon Valley in east-central Alaska. Its ·age is unknown, but the presence of the crinoid Pentacrinus subangularis var. alaska Springer in the same float indicates that beds of Early Jurassic age are present in the area. Otapiria. has been found previously in Upper Triassic to Upper Jurasrsic beds in New Zealand, Lower .Jurassic beds in New Caledonia, and Upper Tria,ssic to Lower Jurassic beds in northea·stern Siberia. INTRODUCTION The recent discovery of a monaticllike pelecypod in northern Alaska prompted the preparation of this paper. This pelecypod was found in a thin unit of organic shale directly overlying Upper Triassic beds and directly underlying, at least loca.lly, Lower Cretaceous beds containing Buchia of Valanginian age. It showed considerable resemblance to the genotype species of Otapiria Marwick (1935, p. 303; 1953, p. 95) from basal Jurassic beds in New Zealand (Trechmann, 1923, p. 270, pl. 15, figs. 6-9; Marwick, 1953, p. 95, pl. 11, figs. 7, 8) and to a species of 0 tapiria. from basal Jurassic beds in northeastern Siberia (Zakharov, 1962, p. 25-29, pl. 1, figs.1-16, pl. 2). Further study showed tha:t the gene·rie assignment to Otapiria was correct and that the genus has a fairly wide distribution in Upper Triassic and Jurassic beds of the Indo-Pacific and Arctic regions. The paper also includes a description of a new genus of another monotidlike pelecypod from beds of late Early Jurassic (Pliensbachian) age in Oregon and California. This pelecypod, herein named Lupherella n. gen., greatly resembles Otapiria and appears to be close~ly related to that genus. Attempts over many years to determine rt.he generic and fa.1nily relationships of L1.tpherella nra.de the writer fam.iliar with the characteristics of Otapiria and led to the identification of 0 tapiria soon after its discovery in Alaska. Many thanks are due to Mr. J. A. Jeletsky of the Geological Survey of Oanada for his aid in locating pertinent Russian publications. Mr. I·an Speden of the New Zeal1and Geological Survey kindly furnished rubber imprints and descriptive data of Otapiria rnwrshalli (Trechmann), the type species of Otapiria. CHARACTERISTICS OF OTAPIRIA The genus Otapiria was defined by Marwick in 1935 (p. 302), and Pseudmnonotis 11wrsha.lli (Trechmann) (1923, p. 270, pl. 15, figs. 6-9) from the Jurassic of New Zealand was designated the type species (pl. 1, figs. 24, 25). Detailed comparisons were made with the pelecypods Entomonotis Marwick (1935, p. 298) and Echinot·is. Marwick's definition, based solely on the type species, was modified slightly in 1953 (p. 95) when he included in the genus two other species from N e"\v Zealand. The modified definition is as follows : Shell of moderate size, obliquely ovate, inequivalve, right valve less inflated than left, posterior wing well developed. Sculpture of numerous close wavy radials, left [sic right] valve with weaker radials or smooth. Right valve with small anterior ear, bounded by a deep groove without a deep notch. This definition does not mention the charaeteristics of the hinge area which Marwick (1935, p. 302) had described in his original definition as follows: Hinge area narrow, edentulous. Ligament set in a strongly and regularly grooved triangular-pit, the base of which is about half the length of the posterior dorsal margin. Left valve with the hinge margin sinused upwards and inwards immediately in front of the umbo, but further forward the margin projects outwards and bears several deep grooves. These characteristics of the hinge area of Otapiria 11wrshalll (Treclnnann) were depicted in drawings (Marwiek, 1935, pl. 36, figs. 28-32, 34, 35) for cmnparisons with similar drawings of Ent01nonotis (Marwick,

The Mesozoic pelecypods Otapiria Marwick and Lupherella Imlay, new genus in the United States