22 



NEW YORK STATE MUSEUM 



no longer accessible and appears to have been overgrown by vege- 

 tation with the drying np of the brook. Seventy-five feet above 

 the Tichenor limestone is another limestone layer lying in the 

 midst of this shale mass. This is here designated as the 



Menteth limestone, and is worthy of special remark for sev- 

 eral reasons. It is a well defined bench mark in these Moscow 

 shales entirely across the map. As a rock it is a compact layer 

 about a foot in thickness and usually very pure but in places it 

 proves to be quite argillaceous and nodular. It is a notable re- 

 pository of the fossils of the fauna and these are very frequently 

 replaced by silica with a degree of delicacy and perfection 

 seldom equaled; perhaps not elsewhere in the paleozoic rocks of 

 the State nor in rocks of ancient date from any locality known to 

 the. writer is this replacement so satisfactory to the student of 

 the biologic problems of paleontology. The etching of the purer 

 part of this layer has afforded a most beautiful series of the 

 species of the fauna and as these are retained not alone in adult 

 condition but from the earliest shell-bearing stage on, the ma- 

 terial has already been the subject-matter of several important 

 treatises on phylogeny, ontogeny and the systematica of different 

 groups of organisms. We may refer to the papers of Beecher on 

 the trilobites and on certain of the corals, to Grabaus investiga- 

 tion of the corals, to the writers publications on some of the 

 brachiopods, etc. An indication of the delicacy of these replace- 

 ments is afforded by some of the shells of the brachiopod Produc- 

 tella in which the hairlike spines on the body of the shell 

 projecting for a length greater than the diameter of the shell 

 itself, are preserved without defect. This Menteth limestone 

 forms the first falls in the ravine at Tichenor point and also in that 

 at Menteth point. It and the shales beneath are well exposed in 

 these places and the shales themselves specially along the shore 

 of the lake between the two points. On the opposite or east side 

 of the lake both shales and limestone are found in Gage creek 

 and Deep run, and again on the east side from Menteth point 

 southward to Foster point. Farther north is an exposure of the 

 limestone and some of the underlying shales at Hope point ravine. 



