. Mesozoic fossils. ousconcentric lines ofgrowth. Hinge den-tition, muscular im-pressions, and pal- FiG. 21.— Unio Ifanaimoensis.—Side view of the only specimen Hal line unknown. known, in 27a.—Dorsal view of the same, also in outline, to shew the Approximateproportionate convexity of the closed valves. dimensions of the Both the figures are of the natural size. «>^ ecimen figured:— Maximum length,sixty-eight millimetres ; greatest height, thirty-seven millimetres ; maxi-mum breadth or thickness, twenty-four millimetres. The slight distortion and somewhat slickensided movement
. Mesozoic fossils. ousconcentric lines ofgrowth. Hinge den-tition, muscular im-pressions, and pal- FiG. 21.— Unio Ifanaimoensis.—Side view of the only specimen Hal line unknown. known, in 27a.—Dorsal view of the same, also in outline, to shew the Approximateproportionate convexity of the closed valves. dimensions of the Both the figures are of the natural size. «>^ ecimen figured:— Maximum length,sixty-eight millimetres ; greatest height, thirty-seven millimetres ; maxi-mum breadth or thickness, twenty-four millimetres. The slight distortion and somewhat slickensided movement to whichthe specimen has been subjected has so displaced the normal position ofthe valves that the marginal outline is not as distinctly defined as mightbe desired, and the beaks are no longer quite opposite. As compared with U. Nanaimoensis, U. ^tt66arc?t is a much more con-vex shell, with distinctly angular or subangular posterior umbonal slopes,and it is much more attenuate posteriorly (op. cit. supra.).. 387 Trigonia Evansana, Meek. Trigonia Evansana, Meek. 1857. Trans. Albany Inst., vol. iv, p. Emoryi, Etheridge. 1861. In Hectors paper On the Geology of the Coun-try between Lake Superior and the Pacific Ocean, Quart. Journ. Geol. Soc. Lond., vol. xvii, p. 432; but not T. Eraoryi, Conrad, , II Etheridge. 18(53. No. 40 of the list of specimens on p. 243 of Capt- Pallisers Official Report on his Explorations in British America in Evansii, Gabb. 18G4. Geol. Surv. Calif., Palagoiit., vol. i, p. 189, pi. 25, fig. Evansi, Meek. 1876. Bull. U. S. Geol. and Geogr. Surv. Terr, vol. ii, No. 4, p. 359, pi. 2, figs. 7, la and Evansana, Whiteaves. 1879. This volume, pt. 2, p. 161; and (1896) Trans. Royal Soc. Canada for 1895, Second Series, sect, iv, p. 114. In 1876, in the second volume of the Bulletin of the United StatesGeological and Geographical Survey of the Territories, Mr. Meek pointedout that his Trigonia Evans
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