14 



numbers. In form they are very variable, no two probably 

 being exactly alike. A number of species have been de- 

 scribed by Hinde from this bed, and they are all illustrated 

 in Part II. They are composed of carbonate and phosphate 

 of lime, and were regarded by Pander and others as the 

 teeth of Mvxinoid fishes. According to Zittel and Rohen*, 

 however, they must be regarded as jaws of Annelids. 



The Coiiodont bed was described and named by Hinder, who dis- 

 covered its position in this and the adjoining sections of Eighteen Mile 

 Creek. He referred it to the Upper Hamilton, which was clearly 

 erroneous, as all its affinities, lithological and palaeontological arc 

 with the Styliolina of the Genesee. This is well shown by the fact that 

 in places the rock loses its distinctive character and is made up of local 

 accumulations of Styliolina fissurelln (Hall). 



Normally the rock is composed of the fragments of crinoid 

 stems, and probably some other calcareous remains, mingled 

 with those offish plates and corneous conodonts. Grains of 

 a green mineral, probably glauconite, are common, and 

 pyrite likewise occurs in considerable abundance. In a thin 

 section, fine quartz grains appear at intervals. Altogether 

 the limestone may be regarded as a fragment al rock, com- 

 posed of the broken remains of organisms, with a very small 

 admixture of transported material. t 



Besides the fossils already mentioned, imperfect specimens 

 of (?) Amhocoelia umhonata (Conrad) have been noticed in 

 the rock, but in general, the shells, if they occur, are so poorly 

 preserved as to be unidentifiable. 



*Zittel and Rohen, " Ueber Conodonten." Sitzungsber. Bay. Akad. Wissensch. 

 Bd. XVI., 1886. 



fOuart. Journ. Geol. Soc. Vol. 35, p. 352, et seq. 



JSince the above has gone to press, mv friend. Dr. Theodore G. White of Columbia 

 College has examined, at my request, thin seetions of the Conodont limestone. He 

 has kindly furnished me with the following note concerning the petrographic 

 character of this rock : "The sections strongly resemble in appearance the silicate 

 bunches occurring in the Archaean or Algonkian limestones at Port Henry, N. Y., 

 mar the contact with the crystalline rocks and ore bodies. The texture of the rock 

 is distinctly crystalline and the mineral fragments do not seem to be water 

 rounded. Magnetite is very abundant through the sections, accompanied by 

 pyrite. Biotite ranks next in abundance and forms a large proportion of the mass 

 Of the rock. .Scattered throughout the sections are long shreads of a fibrous 

 mineral, white in color, scarcely polarizing and giving no interference figure The 

 extinction angle is -J." to 28°, which would indicate that the mineral was probably 

 cyanite. It contains grains of the magnetite, as does also the biotite. Quartz, 

 calcite and hornblende arc present in lesser amounts. One distinct and very 

 perfect spherulite was observed." 



In addition to the above, the rock contains the organic remains alrcadv noted. 



