June 24, 1898.] 



SCIENCE. 



845 



used as a sail ; it was quite as probably or- 

 nainental as protective. This animal be- 

 longs to the primitive reptilian order, 

 Pelycosauria of Cope, but it represented a 

 highly specialized side-branch related to 

 the Ehynchocephalia or Proganosauria, as 

 shown by Baur and Case. 



Interest in the above series of four is 

 ■enhanced by the fact that Professor Cope, 



and Elk, so far as proportions of the body 

 and the shape of the head are concerned. 

 Other models are in preparation, and the 

 series of water-color restorations, which 

 now numbers nineteen, is progressing as fast 

 as the complete skeletons are procured and' 

 prepared, serving as a basis for anatomical 

 study. 



Heney F. OsBOEJsr. 



Fig. 1. — Powell County Natural Bridge. 



shortly before his death, gave Mr. Knight 

 the benefit of many criticisms and ingenious 

 suggestions. 



The latest of this model series is 

 taken from the remarkable skeleton of 

 Cervalees americanus, in the Princeton 

 <3reological Museum. It is upon a larger 

 scale than the preceding, and represents 

 the animal as Scott has described it, namely, 

 intermediate in form between the Moose 



NATURAL ABCBES OF KENTUCKY. 

 Along the western margin of the Eastern 

 Coal Field in Kentucky are a number of 

 ' Natural Bridges,' which it seems to me can- 

 not be explained in any of the ways yet 

 suggested. They have not been formed by 

 the falling in of the roofs of underground 

 streams, by wind erosion, or yet again in 

 the manner presented by the contribution 

 on this subject in the May 20th number of 



