1862.] BIGSBY — CAMBKIAN AND HURONTAN. 43 



large animals, and are probably those of the large Crustaceans whose 

 footprints have just been alluded to. So that we may now-a-days 

 have some small perception of the antique and mysterious interest 

 which is attached to these relics, dragged out of the abysses of time 

 by a young science. 



D. D. Owen and others after him have mentioned, with great 

 surprise, the countless myriads of phosphatic Lingulce buried in the 

 Potsdam Sandstone which forms the walls of the River St. Croix, 

 in Minnesota, not far from its junction with the Mississippi. In 

 the same way Trilobites in incalculable u umbers occupy a bed of 

 Trenton Limestone at Beaufort, Quebec ; all in fragments, and lying 

 flat upon each other. 



c. Primordial Zone. — I have, finally, to request your attention to 

 the great and unexpected abundance of life in the Primordial rocks, 

 the immediate successors of the inhospitable Cambrian. 



About ninety genera of Mollusca, and 250 species (allowing for 

 regional duplicates) met with regionally, are found in this one set of 

 beds (called indifferently Potsdam Sandstone, Lingula-flags, Pri- 

 mordial zone, or, as I believe, Taconic). The Molluscan orders 

 and genera are well represented in this initiatory basement-bed, 

 even up to the most highly organized — excepting the Cephalojjoda , 

 which are entirely absent. 



In this Primordial zone alone, there are twenty-five genera of Tri- 

 lobites, and 114 species ; seventy- three species have been found in 

 Scandinavia alone, partly because this region has been thoroughly 

 examined (by Angelin). 



It must be remembered that vast spaces of the earth's surface have 

 received no attention, and that extensive Silurian districts, such as 

 llussia, Germany (exclusive of Bohemia), Scotland, and Sardinia, 

 have as yet furnished not one indisputable basement-fossil ; while 

 from others, Australia, France, Spain, we have received but one 

 or two. 



We cannot but feel and express great astonishment to see a rich 

 and well-balanced fauna thus spring forth from a Cambrian barren- 

 ness which was nearly absolute, and with a quickness not yet fully 

 explained. Indeed this barrenness is in all probability more ap- 

 parent than real, for, according to Mr. Salter, we are dealing with 

 shore-deposits only, which generally present few species. There 

 may have been, and probably was, a deep-sea fauna*. 



All that has now been stated may well prepare our minds to re- 

 cognize a living nature in the Laurentian, or fundamental gneiss- 

 rocks, equally diversified and plentiful. We may not have found, at 

 this moment, the very forms themselves, but their residuary elements 

 are there in vast abundance. 



* With a group or commonwealth of living creatures in the Primordial zone, 

 so well furnished and peopled in every department of Molluscan life, some re- 

 quiring deep or shallow waters, some only flourishing in moist sands or tangled 

 seaweed, and others on rocks above low water, is it not probable that the univer- 

 sal, shallow levels frequently attributed by continental authors to the earliest 

 Silurian period have only existed in imagination ? 



