by the whole of the rocks from the base of the Utica slate, downward, with the probable exception of the Potsdam sandstone; while he conceived, partly on lithological grounds, that the Utica and Hudson-River groups represented the Llandeilo and Caradoc, or the Lower Silurian of Murchison [loc. cit. pages 20, 29, 31]. The origin of the Cambrian and Silurian controversy, and the errors by which the Llandeilo and a part of the Caradoc had by Murchison been classed as a series distinct from the Bala group, were not then known; but in a note to this report [page 20,] Hall informs us of the declaration of Murchison, already quoted from his address of 1842, that the Cambrian, so far as then known, could not, on paleontological grounds, be distinguished from his Lower Silurian.

Emmons meanwhile had examined in eastern New York and western New England a series of fossiliferous rocks, which on lithological and stratigraphical grounds, he regarded as older than any in the New York system; a view which had been previously maintained by Eaton. Holding, with Hall, that the lower members of the New York system were the equivalents of the Upper Cambrian of Sedgwick, he looked upon the fossiliferous rocks which he placed beneath them, as the representatives of the Lower Cambrian. By this name, as we have seen, Sedgwick, in 1838, designated all those uncrystalline rocks of North Wales which he subsequently divided into Lower and Middle Cambrian, and which lie beneath the base of the Bala group. When Murchison, in 1842, in his so often quoted declaration, asserted that "the term Cambrian must cease to be used in zoological classification, it being in that sense synonymous with Lower Silurian," he was speaking only on paleontological grounds, and, disregarding the great Lower and Middle Cambrian divisions of Sedgwick, had reference only to the Upper Cambrian. This however was overlooked by Emmons, who feeling satisfied that the sedimentary rocks which he had examined in eastern New York were distinct from those which he, with Hall, regarded as corresponding to the Bala group or Upper Cambrian, (the Lower Silurian of Murchison), and probably equivalent to the inferior portions of Sedgwick's Cambrian; and supposing that the latter term was henceforth to be effaced from geology (as indeed was attempted shortly after, in the copy of Sedgwick's map published in 1844 by the Geological Society) devised for these rocks the name of the Taconic system, as synonymous with the Lower

(and Middle) Cambrian of Sedgwick. These conclusions were set forth by him in 1842, in his report on the Geology of the Northern District of New York [page 162]. See also his Agriculture of New York [I, 49] the fifth chapter of which, "On the Taconic system," was also published separately in 1844; when the presence of distinctive organic remains in the rocks of this series was first announced.

Meanwhile to Prof. Hall, after the completion of the survey, had been committed the task of studying and describing the organic remains of the state, and in 1847 appeared the first volume of his great work on the "Paleontology of New York." Since 1842 he had been enabled to examine more fully the organic remains of the lower rocks of the New York system, and to compare them with those of the old world; and in the Introduction to the volume just mentioned [page xix] he announced the important conclusion that the New York system itself contained an older fauna than the Upper Cambrian of Sedgwick. According to Hall, the organic forms of the Calciferous and Chazy formations had not yet been found in Europe, and our comparison with European fossiliferous rocks must commence with the Trenton group. He however excepted the Potsdam sandstone, which already, in 1842, he had conceived to be below the Upper Cambrian of Sedgwick, and now regarded as the probable equivalent of the Obolus or Ungulite grit of St. Petersburg. Thus Emmons, in 1842, asserted, on lithological and stratigraphical grounds, the existence, beneath the base of the New York system, of a lower and unconformable series of rocks, in which, in 1844, he announced the discovery of a distinctive fauna. Hall, on his part, asserted in 1842, and more fully in 1847, that the New York system itself held an older fauna than that hitherto known in the British rocks.

It is not necessary to recall in this place the details of the long and unfortunate Taconic controversy, which I have recently discussed in my address before the American Association for the Advancement of Science in August, 1871. It is however to be remarked that Hall, in common with all other American geologists, followed Henry D. Rogers in opposing the views of Emmons, whose Taconic system was supposed to represent either the whole or a part of the Champlain division of the New York system; which included, as is well known, all of the fossiliferous rocks up to the base of the Oneida conglomerate (and also this

latter, according to Emmons); thus comprehending both the first and the second paleozoic fauna; as shown in the table on page

312.

Emmons, misled by stratigraphical and lithological considerations, complicated the question in a singular manner, which scarcely finds a parallel except in the history of Murchison's Silurian sections. Completely inverting, as I have elsewhere shown, the order of succession in his Taconic system, estimated by him at 30,000 feet, he placed near the base of the lower division of the system the Stockbridge or Eolian limestone, including the white marbles of Vermont; which, by their organic remains, have since been by Billings found to belong to the Levis formation. A large portion of the related rocks in western Vermont and elsewhere, which afford a fauna now known to be far more ancient than that of the Lower Taconic just referred to, and as low if not lower than anything in the New York system, were, by Emmons, then placed partly near the summit of the Upper Taconic, and partly not only above the whole Taconic system, but above the Champlain division of the New York system. Thus we find in 1842, in his Report on the Geology of the Northern District of New York (where Emmons defined his views on the Taconic system), that he placed above this latter horizon, both the green sandstone of Sillery near Quebec, and the red sandrock of western Vermont, (which he then regarded as the representatives of the Oneida and the Medina sandstones,) and described the latter as made up from the ruins of Taconic rocks [pages 124, 282]. In 1844-1846, in his Report on the Agriculture of New York [I. 119], he however adopted a different view of the red sandrock, assigning it to the Calciferous; and in 1855, in his "American Geology" [ii. 128], it was regarded as in part Calciferous and in part Potsdam. In 1848 Prof. C. B. Adams, then director of the Geological Survey of Vermont, argued strongly against these latter views, and maintained that the red sandrock directly overlaid the shales of the HudsonRiver group and corresponded to the Medina and Clinton formations of the New York system. [Amer. Jour. Sci. II, v. 108.] He had before this time discovered in this sandrock, besides what he considered an Atrypa, abundant remains of a trilobite, which Hall, in 1847, referred to the genus Conocephalus (Conocoryphe), remarking at the same time that inasmuch as this genus was (at that time) only described as occurring in

"graywacke in Germany" and elsewhere, no conclusions could be drawn from these fossils as to the geological horizon of the rocks in question. [Ibid. II, xxxiii, 371.] In September, 1861, however, Mr. Billings, after an examination of the rocks in question, pronounced in favor of the later opinion of Emmons, declaring the red sandrock near Highgate Springs, Vermont, containing Conocephalus and Theca, to belong to the base of the second fauna "if not indeed a little lower," and to be "somewhere near the horizon of the Potsdam." [Ibid. II, xxxii, 232.]

The dark colored fossiliferous shales which were asserted, both by Adams and by Emmons, to underlie this red sandrock, were, by the former, as we have seen, regarded as belonging to the Hudson-River group, while by the latter they were described as an upper member of the Taconic system; which was here declared to be unconformably overlaid by the red sandrock, a member of the New York system. These slates, a few years before, had afforded some trilobites, which after remaining in the hands of Prof. Hall for two years or more, were in 1859, described by him in the 12th "Report of the Regents of the University of New York," as Olenus Thompsoni and O. Vermontana. He soon however found them to constitute a distinct genus, for which he proposed the name of Barrandia, but finding this name preoccupied, suggested in 1861, in the 14th "Regents' Report," that of Olenellus, which was subsequently adopted by Billings, in 1865. [Paleozoic Fossils, pages 365, 419.] In 1860, Emmons, in his "Manual of Geology," described the same species, but placed them in the genus Paradoxides, as P. Thompsoni and P. Vermontana. Hall had already, in 1847, in the first volume of his Paleontology of New York, referred to Olenus the Elliptocephalus asaphoides of Emmons, and also a fragment of another trilobite from Saratoga Lake; both of which were described as belonging to the Hudson-River group of the New York system, or to a still higher horizon. The reasons for this will appear in the sequel. The Elliptocephalus, with another trilobite named by Emmons Atops, (referred by Hall to Calymene, and subsequently, by Billings to Conocoryphe,) occurs at Greenwich, New York. These were by Emmons, in his essay on the Taconic system (in 1844), described as characteristic of that system of rocks.

A copy of the Regent's Report for 1859 having been sent by Billings to Barrande, this eminent paleontologist, in a letter

addressed to Prof. Bronn of Heidelberg, July 16, 1860 [Amer. Jour. Sci. II, xxxi, 212], called attention to the trilobites therein figured, and declared that no paleontologist familiar with the trilobites of Scandinavia would "have hesitated to class them among the species of the primordial fauna, and to place the schists enclosing them in one of the formations containing this fauna. Such is my profound conviction, etc." The letter containing this statement had already appeared in the American Journal of Science for March, 1861, but Mr. Billings in his note just referred to, on the fossils of Highgate, in the same Journal for September of that year, makes no allusion to it. In March, 1862, however, he returns to the subject of the sandrock, in a more lengthy communication [Ibid II, xxxiii, 100), and after correcting some omissions in his former note, alludes in the following language to Mr. Barrande, and to the expressed opinion of the latter, just quoted, with regard to the fossils in question and the rocks containing them : "I must also state that Barrande first determined the age of the slates in Georgia, Vermont, holding P. Thompsoni and P. Vermontana." He adds "at the time I wrote the note on the Highgate fossils it was not known that these slates were conformably interstratified with the red sandrock. This discovery was made afterwards by the Rev. J. B. Perry and Dr. G. M. Hall of Swanton."

Mr. Billings now blames me [Canadian Naturalist, new series, vi, 318] for having written in my address of last year, with regard to the Georgia trilobites, first described as Olenus by Prof. Hall, that Barrande "called attention to their primordial character, and thus led to a knowledge of their true stratigraphical horizon." I had always believed that the letter of Barrande and the explicit declaration of Mr. Billings, just quoted, contained the whole truth of the matter. My attention has since been called to a subsequent note by Mr. Billings in May, 1862, [Ibid II, xxxiii, 421] in which, while asserting that Emmons had already assigned to these rocks a greater age than the New York system, he mentions that in sending to Barrande, in the spring of 1860, the Report of Prof. Hall on the Georgia fossils, he alluded to their primordial character, and suggested that they might belong to what Mr. Barrande has called a colony' in the rocks of the second fauna. This is also stated in a note by Sir William Logan in the preface to the Geology of Canada [page viii.] As the genus Olenus, to which Prof. Hall had referred