14 



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

 being exactlv alike. A number of speeies have been de- 

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

 in Part II. Thev 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, thev must be regarded as jaws of Annelids. 



The Couodont bed was described and uanied by Hiudet, nyIio dis- 

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

 Creek. He referred it to the Up]ier Hamilton, which was clearly 

 erroneous, as all its affinities, lithological and palaeontological are 

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

 in ])]accs the rock loses its distinctive character and is made tip of local 

 accumulations of Styliolina fissiirelln (Hall). 



Normallv the rock is composed of the fragments of crinoid 

 stems, and probably some other calcareous remains, mingled 

 \vith those offish plates and corneous conodonts. Grains of 

 a gTeen mineral, probabh' glaitconite, are common, and 

 pvrite likewise occurs in considerable abundance. In a thin 

 section, fine quartz grains appear at intervals. Altogether 

 the limestone may be regarded as a fragmental rock, com- 

 posed of the broken remains of organisms, \vith a very small 

 admixture of transported inaterial.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." Sitzungslier. Bay. Akad. Wissensch. 

 Bd. XVI., 1886. 



IQiiart. Jotirn. Geol. Soc. Vol. .So, p. 352. et seq. 



tSiiice the above has gone to press, my friend, Dr. Theodore G.White of Columbia 

 College has examined, at my request, thin sections of the Couodont limestone. He 

 has kindly furnished me ^vith the following note concerning the petrographic 

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

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

 near 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. yinf^netite is very abundant through the sections, accompanied by 

 pvrite. 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, \vhite in color, scarcely polarizing and giving no interference figure. The 

 extinction angle is 25° to 28°, which \vould indicate that the mineral was probably 

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

 ctilcite and hornblende are present in lesser amounts. One distinct and very 

 perfect spherulite ■was observed." 



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



