THE PALEONTOLOGIC RECORD 5 8 5 



changes, of movements, of trend and tendency among living things 

 ranging over a period of time equal to many millenniums. 



Another life record of especial interest, typical of many scattered 

 up and down the land areas of the globe, is furnished by the Osage 

 division of the Mississippian at Burlington and Keokuk. Of one group 

 of crinoids, the Camerata, these Mississippian limestones have yielded 

 about 250 species, and of other groups a number about equally as great. 

 The beauty and perfection of the individual specimens can be ap- 

 preciated only by those who have had the good fortune to see the superb 

 collections of Wachsmuth and Springer. Crinoids flourished here in 

 such numbers that beds of limestone 150 feet in thickness are built 

 practically of crinoidal remains and nothing else. The time repre- 

 sented was long enough to allow of a series of modifications of such ex- 

 tent that the crinoid fauna of the Upper Burlington is very distinct 

 from that of the lower beds of the same formation, while the fauna of 

 the Keokuk differs from both. Here again the paleontologist is 

 favored, not only with a wealth of material, but with an opportunity to 

 note the trend and tendency of things. This was the time of greatest 

 development, of highest prosperity, among camerate crinoids. But in 

 the midst of this prosperity the trained paleontologist may discover 

 signs of degeneration, the prophecy of speedy extinction. The law 

 enunciated by Beecher and quoted by Professor Woodward in his ad- 

 dress before the geological section of the British Association at its 

 meeting in Winnipeg last summer, is well exemplified in the Missis- 

 sippian history of this particular group of crinoids. The tendency 

 among any division of skeletal-bearing animals to run to extravagant 

 ornamentation in the way of ribs, nodes, spines or other excesses of 

 dead, useless, skeletal matter, is something that precedes and presages 

 the decline and death of the race. Even in the Upper Burlington the 

 skeleton of the crinoids is heavier than in the Lower; stronger nodes 

 on the plates are produced; more arm plates are incorporated in the 

 dorsal cup; the animals are weighted down with useless matter. This 

 tendency is carried to extremes in the Keokuk limestone, a fact well 

 exemplified by the species figured on plate 15 of Hall's " Geology of 

 Iowa," Volume I., part II. In these species the development of 

 massive spines and heavy nodose plates reaches its maximum. The 

 race has come to the end of its career. When the Keokuk closes, only a 

 few of the simpler forms of the Camerata survive, and even these 

 shortly disappear. The paleontologist sees the operation of the same 

 law, the same trend and tendency, among the Cretaceous Ammonoids; 

 in many other groups of animals it is as clearly manifest; but it would 

 not be profitable, before such a body as this, to carry the discussion 

 farther, even if the limits of the paper permitted. Let me close by 



vol. rxxvi. — 40. 



