l8 I>.\\ FM'okl ACADEMY OF NATURAL SCIENCES. 



These two exposures, in extent of surface, exceed ours a hundred, if 

 not many hundred times. So much for extent of rock. 



Another equally important fact is its prevailing fossiliferous charac- 

 ter. In many places, limestones and shales are absolutely crowded 

 with fossils, many of which are in an excellent state of preservation. 

 Professor Rominger writes in reference to the shoals near Thunder Bay 

 Island: "The exuberance of fossils is most beautifully exhibited. One 

 sailing on them can see for miles the whole bottom paved with corals 

 in convex lumps, from a few inches to some feet in diameter, their white 

 sparry substance contrasting beautifully with the dark limestone which 

 incloses them."* 



Professor Winchell says of a certain coral: "Fine specimens of this 

 coral can be collected in any quantity, even to a shipload." t 



With such extensive exposures of rock, in many portions crowded 

 with fossils, we ask as to the number of species that are found. If our 

 meagre exposure, measured by a few rods, affords two hundred and 

 forty-six species and more, may we not expect a proportionate increase 

 in number with miles of exposure, its profusion of fossils, two of the 

 most accomplished geologists of the day engaged in the survey, and the 

 wealth of the whole State of Michigan to back them in their work? 

 What is the result? Professor Winchell thus writes: "The table which 

 follows embraces a list of all the fossils thus far collected, including the 

 collections of my recent survey, and those heretofore made by State 

 authority."^: That list furnishes ninety-two species. In addition to 

 these. Professor Rominger enumerates seventy-five more. Thus the 

 results of the two geological surveys of Michigan are one hundred and 

 sixty-seven species. In other words, the whole State of Michigan has 

 furnished not far from two-thirds as many species as are found in our 

 few small quarries and neighboring exposures. Is it probable? 



The same survey furnishes us with another equally pertinent illustra- 

 tion. A family of corals, known as the CyathopliyUuitc, exists in the 

 Hamilton of Northern Michigan, at times in as wonderful state of per- 

 fection as when the polyp lived in its cell. In this locality the whole 

 internal cavity is filled with foreign material which cannot be removed 

 without injury to the structure, and yet on this internal portion, more 

 than any external character, the identification of this class of corals de- 

 pends. Of this one family of the Cyathophyllida', in its two members of 



♦Geological Survey of Michigan, by Professor Rominger, Vol. III., p. 47. 

 f Report on the Grand Traverse Region, by Professor Winchell, p. 41. 

 t Report on the Grand Traverse Region, p. 85. 



