12 



The Styliolina (Styliola) layer was first described by Clarke* from 

 ( Ontario county and adjoining districts. It there lies about twenty feet 

 above the base of the Genesee formation and varies in petrographical 

 character in its different outcrops. Clarke has estimated that the rock 

 contains at least 40,000 individuals of the Styliolina to a cubic inch, 

 which, when the whole extent of this limestone lied is taken into 

 consideration, indicates an almost incredible numerical development of 

 these shells. According to Clarke's investigations! the shells have been 

 Idled by calcic carbonate, deposited in even concentric layers on the 

 inside of the shell, a longitudinal section of a shell thus having the 

 appearance of vein infiltration. Many shells also have an external 

 coating of calcic carbonate, which like the internal filling, has a 

 crystalline structure.:!: 



Plant remains are not uncommon in the Styliolina 

 stratum, these being usually the trunks and other woody 

 parts of coniferous trees, most of which may probably be 

 referred to the genus Dadoxylon ( Unger ). These tree trunks 

 are supposed by Sir William Dawson to have been carried 

 by river floods into the sea, like modern drift wood, and 

 there buried in the growing lime stones and shales, and 

 finally to have been replaced by mineral matter. 



The genus Dadoxylon (Unger) is referred by Dawson to the yews,§ 

 while Shenkll classes it with Cordaites. Speaking of these trees Dawson 

 saysfi : "It" (the wood) " often shows its structure in the most perfect 

 manner in specimens penetrated by calcite or silica, or by pyrite, and in 

 which the original woody matter has been resolved into anthracite or 

 even into graphite. These trees have true woody tissues, presenting 

 that beautiful arrangement of pores or thin parts enclosed in cup like 

 discs, which is characteristic of the coniferous trees, and which is a 

 great improvement on the barred tissue" (of lycopodiaceous trees) ". . 



affording a far more strong, tough and durable wood, such 



as we have in our modern pines and yews." A remarkable fossil wood 

 was described by Dawson under the name Syringoxylon rnirabile°, from 

 a small fragment collected by Prof. Hall — "from a limestone in the 

 upper part of the Hamilton group" at Eighteen Mile Creek. The 

 limestone referred to is probably the Styliolina, or perhaps the 

 ' Conodont." The wood is that of an angiospermous exogen, the 



•J. M. Clarke, Bull. 16, U. S. Geol. Surv., p. 14. 

 tLoc. cit., p. 15. 



JFor a detailed description of the interesting optical phenomena exhibited in 

 sections of these shells, see Clarke, Bull. 16, 1'. S. Geol. Surv., p. 16. 

 gGeol. Hist, of Plants, 1888, p. 78. 

 HZittel Handb., d. Pal. 2te Abth., p. 870. 

 HLoc. cit., pp. 79 and 80. 

 °Quart. Journ. Geol. Soc, Vol. XVIII., p. 305, 1862. 



