BIGSBT PALEOZOIC ROCKS OF NEW YOEK. 



265 



Wales, especially the Brachiopoda — partly, as has already been said, 

 from a small but general infiltration of lime among the sediments of 

 the latter region. 



d. Fossils in Calcareous and in Non-calcareous strata. — The sum- 

 maries contained in Tables VII. and VIII. wiU give much additional 

 information. They have been carefully prepared from the general 

 Tables of matrices in the New York and Welsh basins. 



Table VII. shows the number of fossils which have exclusively 

 either calcareous or non-calcareous habitats. The areas of New York 

 and Wales being so different in size and so remote from each other 

 (the flora likewise not being the same), we do not expect to find in 

 them the same number of fossils ; but we are interested in observing 

 a general similarity of matrix and of numerical proportions in all 

 the orders of animal life until we come to the Lamellibranchiata, 

 Gasteropoda, and Cephalopoda. Among these we find the fossils in 

 non- calcareous beds greatly multiplied in Wales, — so much so as to 

 be in Dimyaria in the ratio of sixty-nine to fifty-seven calcari- 

 colous, and in Heteropoda as twenty-four to nineteen. Table VIII. 

 exhibits the proportions of species-life as found in the sedimentary 



Table VTII. — Species-Life, numerically, as appearing in the 



Sedimentary Habitats in New YorTc and Wales, 



(Reduced fi*om Tables Y. and VI.) 



Silurian Sediments. 



Fossils, by Species. 

 (Appearances). 



NEW YORK. 



( Sniceous Conglomerate 



Siliceous Grit 



SiHceous Sandstone ... 

 \ Argillaceous Sandstone 



Iron-ore 



Mudstone 



Carbonaceous Shale ... 



o 



^ Calcareous Sandstone 



Calcareo-argillaceous Shale 



Argillo-calcareous Shale .. 



sniceous Limestone 



Argillaceous Limestone 



(^Limestone 



25 



67 

 10 



— 102 

 36 



102 

 156 



8 

 387 

 133 



— 822 



WALES. 



42 



61 

 142 

 250 



160 

 69 



— 724 

 267 

 220 

 173 



306 

 37 



1003 



Total 



924 



1727 



beds of the two countries. It teUs us that their fossils, though 

 harmonizing in important respects, differ greatly in their numbers 

 as occupants of the same sediment. Thus New York at present 

 is supposed to have no Silurian fossils in siliceous conglomerate 

 or grit ; while Wales possesses many, and indifferently in all the 

 stages of the system. In no case is this diversity more striking 

 than in those of calcareous sandstone and of pure limestone, because 

 the ages and conditions of deposit were different in the two coun- 



