Haichf.r : Tin: Jirassu Dinosaur Deposits. 335 



abandoned quarries of Marsh and Cope as well as making some further 

 examinations with a view to determining, if i)ossible, the vertical dis- 

 tribution of dinosaur remains throughout the beds. After a very 

 superficial examination it became apparent that there were several dis- 

 tinct fossil -bearing horizons and that this locality more than any other 

 offered very superior advantages for securing materials which would 

 be of exceptional value in tracing the development of the different 

 dinosaurian genera, owing to the various horizons at which the fossils 

 are to be found and the ease with which the relative position of these 

 various horizons can be determined. With this end in view rather 

 than for the sole purpose of obtaining dinosaur bones, steps were at 

 once taken to reopen the old quarries ;S0 long abandoned and to estab- 

 lish new horizons. 



The Marsh Quarrv. 



Under the above name the locality most worked by Professor 

 Marsh is referred to and from it were secured all the skulls and several 

 of the most complete skeletons of Jurassic dinosaurs figured and de- 

 scribed by him. He only abandoned it after the expense necessary to 

 operate it had become so great, through the amount of material to be 

 removed from above the bone- bearing horizon, that it was deemed no 

 longer profitable. Both Mr. Felch and Mr. Smith, who had last 

 worked the quarry for Marsh, represented to the writer that bones 

 were seemingly just as abundant at the close of operations as at any 

 time during the progress of the work. After this assurance from these 

 gentlemen I decided to reopen this quarry at once. I was further led 

 to this decision by the fact that the bone-bearing horizon in the quarry 

 lies in the trough of a basin-shaped lens of sandstone, the bottom of 

 which evidently owes its configuration to its having been deposited 

 in a rather deep excavation in the surface of the underlying clays, which 

 then formed the bottom of some stream or other shallow body of water. 

 This basin, enclosed by an impervious stratum of clay, caused the for- 

 mation of a bog or bed of quicksand thus endangering the lives of 

 such animals as chanced to wander that way. The position occupied 

 by this lens of sandstone in reference to the surface of the underlying 

 clays is shown in the photograph of the front of the quarry reproduced 

 in Fig. 2. The work of reopening the quarry was commenced No- 

 vember I, 1900, and the bone-bearing horizon was laid bare over a 

 strip sixteen feet wide and running the entire length of the quarry, or 

 about seventy feet. At the upper end fully twenty feet of rock had 



