. A dictionary of the fossils of Pennsylvania and neighboring states named in the reports and catalogues of the survey ... Paleontology. Microdiscus punctatus, (Salter, Q. J. G. S. London, 1864, XX, 237, pi. 13, fig. 11—Whiteaves, Am. J. Sc. 1878, xvi, 'i^'^b,—Micro- discus pulchellus^ Hartt, No. 13 of J list sent to Dawson.) Walcott, Bull. U. S. G. S. No. 10, page 24, plate 2, figs. 1, la, 15, head shields (gla- bellas) showing variations of form and making, enlarged four times. Fig. 1<?, tail piece (pygidium) en- larged three times.—Middle Cam- hrian {Saint John) formation, New Brunswick,
. A dictionary of the fossils of Pennsylvania and neighboring states named in the reports and catalogues of the survey ... Paleontology. Microdiscus punctatus, (Salter, Q. J. G. S. London, 1864, XX, 237, pi. 13, fig. 11—Whiteaves, Am. J. Sc. 1878, xvi, 'i^'^b,—Micro- discus pulchellus^ Hartt, No. 13 of J list sent to Dawson.) Walcott, Bull. U. S. G. S. No. 10, page 24, plate 2, figs. 1, la, 15, head shields (gla- bellas) showing variations of form and making, enlarged four times. Fig. 1<?, tail piece (pygidium) en- larged three times.—Middle Cam- hrian {Saint John) formation, New Brunswick, and New Foundland.—M. C. Microdiscus quadricostatus, (Properly a young Irinu- cleus.) Emmons, American Geology, Vol. 1, part 2, page 116, plate 1, fig. 8, enlarged ahout five diameters, Wolcott, in Bull. U. S. G. Sur. No. 30, page 152, says, Emmons' genus Microdiscus was founded on a speci- men of Trhiucleus. — Barrande thought Emmons' minute forms might be the young fry of some large trilobite like Trinucleus. (Salter.)—Now, many of these minute species are known {jpunctatus^ speciosus, etc.,) and grouped as Microdiscus^ midway between the Agnos- ^^^5 and the Conophrys groups. Pemphigaspis iullata (Hall, 16th An. Rt. p. 221) is closely related.—Emmons' specimens were found in the White fragile [H. River) shales. His name Microdiscus cannot be applied to his specimens; but it is retained for all the minute Cambrian species. (Walcott.) Microdiscus speciosus, (Ford. 1873, Am. J. S. VI, p. 137, fig. 2 a, I. XIII p. 141.) Wal- cott, Bulletin U. S. G. S. No. 30, ^ page 154, plate 16, fig. 3, Za^ top I and side, enlarged twice; 3b, tail (pygidium) enlarged twice. Fig. 3c. very perfect head from Troy.—Lower Camlrian {Geor- gian) formation in Canada, and not rare near Troy, N. Y.—. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfec
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