THE TEPEE ROCK AND ITS FOSSILS. 337 



ing shale and of one of the ordinary concretions of the shale, the de- 

 terminations showing that the tepee rock does not differ materially in 

 composition from the concretions, and that the argillaceous material is 

 practically identical with the shale. This permits us to regard the argil- 

 laceous material as included shale, and therefore an impurity rather than 

 an essential constituent of the tepee rock. 



The rock is of coarse texture, breaks with rough fracture, and its gen- 

 eral color is a light, warm gray. It is full of fossil shells, and the micro- 

 scope shows that they are imbedded in a matrix which is composed of 

 fragments of shell, water-worn grains of calcite, foraminifera and clay. 

 Cross-sections of Lnclaa shells show that the original shell structure re- 

 mains, although the lime of the shell has been recrystallized into calcite. 

 Inside of the shell wall there is a band of radiating crystals of calcite, 

 showing well marked spherulitic structure. The calcareous ooze which 

 must have at first occupied the central cavit}'' of the shell has recrystal- 

 lized into very pure calcite, leaving the clay impurities at one side of 

 the shell. This central calcite crystal is the same individual which has 

 replaced the lime of the shell, for the two parts extinguish together, the 

 cleavage cracks extend from the center through the outside, and when 

 the spherulitic band is faulted the clear calcite is continuous through 

 the cracks. Experiments showed the spherulitic layer to be slightly 

 less soluble in dilute hydrochloric acid than the clearer calcite. 



FOSSILS. 



The fauna is marine. By far the most abundant molluscan species is 

 a Lucinrij and this may indeed be regarded as a leading constituent of 

 the rock. Inoceramus ranks second, and cephalopods occur in notable 

 variety. Foraminifers appear in all microsections, and the genera Glo- 

 bigerina, Roialia, Plecanifnn and Saccamina were recognized. Fossil w^ood 

 was found in several different cores. The following is a list of the mol- 

 luscan species as determined l)}^ Mr T. W. Stanton : 



Ostrea iiiornata, M. and H. 



Inoceramus crispii, var. barahini, Morton. 



Inoceramus vanvxemi, M. and H. 



Inoceramus sagcmis, Owen. 



Luchia occidentalis, var. venfricosa, M. and H. 



Thetis circnlaris, M. and H. 



Anchnra {Drepanorhibia) americana, E. and S. 



Nautilus dekayi, Morton. 



Baculites ovatus, Say. 



Baculites compressiis, Say. 



Scaphites nodoxus, Owen(?) 



Sf-nphitt'S nodoHus, var. quadraiKjnlaris, M. ami H. 



Scaphites nodosus, var. hrrrin, Meek. 



Ptychoceras crassum, Whitfield. 



