Cl PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



even then well-marked, as he was the first to point out to me the 

 remarkable veins of sulphate of strontian (Celestine) in the island of 

 Lough Erie, now called " Strontian Island ; " and I do not forget that 

 he required me to forward to him a correct drawing of a trilobite 

 from Lake Huron, then in my possession. He has lately been most 

 industriously occupied in preparing a general Geological Map of 

 North America, and (whilst engaged in that laborious task) having 

 been doubtless led to observe and estimate the difficulty of wading 

 through so many detached reports drawn up by independent United 

 States geologists, has wished to spare others a similar necessity. 

 His first paper treats of the mineralogical and fossil characters of 

 the Palaeozoic strata of New York, and divides itself into the follow- 

 ing heads : — " Mineral character," " Mode of transition," " Place," 

 " Position or dip," " Thickness," " Fossils common and typical," 

 " Fossils occurrent in Europe," " Fossils recurrent in New York." 



As Dr. Bigsby's principal object is to form a standard of compa- 

 rison, by which the palaeozoic strata of New York may be brought 

 into relation with those of other districts, he has drawn up tables, 

 constructed from the writings of many preceding authors, both 

 American and European ; and, though he admits that some revision 

 of the American fossils is still required, it cannot be doubted that 

 his work will be a great aid to those who hereafter may undertake 

 the systematic correlation of the palaeozoic formations of the whole 

 earth. Admitting for the present the minute subdivisions of the 

 palaeozoic formations by the American geologists to be correct, he 

 proceeds to describe seriatim the seventeen subdivisions of the Silu- 

 rian from the Potsdam Sandstone to the Upper Pentamerus Lime- 

 stone, and the twelve subdivisions of the Devonian from the Oris- 

 kany Limestone to the Old Red Sandstone, under each of the dis- 

 tinctive heads I have enumerated. In this respect it is curious to 

 observe the approximative horizontality even in the lower palaeozoic 

 formations, though occasionally and very partially disturbed by local 

 causes. The two terms, occurrent and recurrent fossils, represent, 

 1st, the correlation in fossils with European strata, and, 2nd, the 

 repetition of the same fossils in successive American strata. In the 

 Potsdam sandstone (the lowest member of the Silurian system), only 

 one fossil is represented as occurrent in Europe and none as recur- 

 rent in America ; but in ascending, the number both of occurrent 

 and recurrent species increases ; and the latter occasionally pass up 

 to a much higher level. It cannot be doubted that all these con- 

 siderations are of the highest interest ; and when the fossils of Ame- 

 rica have been carefully compared with those of Europe, specimen 

 with specimen, not figure with figure, so as to separate varieties 

 from species and enable the geologist to avoid the introduction 

 of old species into the catalogue as new, a correlation effected on the 

 principles adopted by Dr. Bigsby will lead to a more correct know- 

 ledge of this great section of the palaeozoic formations. In his 

 second paper he discusses the stratigraphy and classification of the 

 whole series of the palaeozoic rocks, and agrees almost entirely with 

 M. De Yerneuil, the modifications proposed by himself being prin- 



