THE PALEONTOLOGIC RECORD 583 



parts were supported or protected by a stony skeleton of some kind; 

 no parts of the skeletal structure were too minute to be kept practically 

 unaltered to the smallest microscopic detail; no period of time has 

 been so long that the records of the large or the small things of life 

 were necessarily obliterated. The shells of such minute and delicate 

 things as radiolaria and foraminifera, on the one hand, and that king 

 of invertebrates, the giant Camaroceras, on the other, have all been 

 kept through the ages with equal fidelity. The hinge characters of 

 the brachiopods, their internal arm supports, their spires and loops, the 

 distribution of the ramifying blood channels in the mantle, the surface 

 markings of every rank and grade down to the smallest which can be 

 observed only with the lens, and the microscopic structure of the shell 

 itself, are other examples of the faithfulness with which details, how- 

 ever insignificant in point of magnitude, have been guarded, protected, 

 preserved. Strangely enough, in respect to a very large proportion of 

 the animal remains buried in the ancient sediments it looks as if time 

 had been standing still; it has neither marred nor destroyed. The 

 organic remains from the Ordovician formations are quite as perfectly 

 preserved as those from the Tertiary. 



The profusion of the life of the ancient seas is as much a source of 

 surprise as the detailed perfection of the record. In the Mississippi 

 Valley limestones constitute a very large proportion of the sedimentary 

 rocks, and it is unnecessary to say that these limestones record the life 

 and death of countless myriads of organisms. In some cases the waters 

 of the old seas were comparatively quiet, and the shells or other hard 

 parts, undisturbed and unbroken, remain in the positions they occu- 

 pied when the individuals they represent were alive. There is a bed 

 of marly shale carrying many thin lenses of limestone, lying between 

 the Platteville and the Galena, from 60 to 70 feet above the base of 

 the Mohawkian, and these lenses are made up in large part of un- 

 broken brachiopod shells. On the surface of one of these slabs, in an 

 area measuring 35 square inches, one may count more than 60 perfect 

 specimens of Dalmanella subcequaia and Orthis tricenaria. The rate 

 is about 290 individuals to the square foot. The number on a square 

 mile of such sea bottom runs up into the billions. The number of 

 individuals of the species Pentamerus oblong us that swarmed on the 

 bottom of the Xiagaran sea is strikingly demonstrated in every paleon- 

 tological museum. The wide geographic range of this species is well 

 known; its range in time was such as to make possible the accumula- 

 tion of beds of limestone, 70 feet in thickness, from the detritus of 

 its broken shells. Like other persistent or widely ranging species, it 

 gave rise to a very large number of varietal forms, some of which have 

 been described as specifically distinct. 



The Devonian formations furnish similar evidence of the wonder- 



