258 WARD 



School of Mines of the University of Wyoming, at Laramie, 

 Wyoming. They are for the most part fragments, but there 

 are a few entire trunks. The three largest, Nos. 500.1, 500.2, 

 and 500.65, though all present, are each broken in two pieces 

 which fit perfectly together. In a number of cases comple- 

 mentary parts had been detected and unfortunately for their 

 convenient study, glued together. In others such complements 

 had been recognized and given the same number. It was ob- 

 vious, however, that many fragments that belong together had 

 not been identified, and much time was spent in finding and 

 joining these counterparts. This study ultimately resulted in 

 finding about twenty-five such cases. In addition to these there 

 are a number which, although they do not actually fit together, 

 nevertheless evidently belong to the same trunk, the structure 

 being continuous and explicable on the assumption of the loss 

 of intermediate portions. Putting these two classes together, 

 the number of independent trunks and fragments is reduced to 

 61. In several cases more than two fragments belong together, 

 for example, in three cases there are three, and in two cases 

 there are five separately numbered pieces of the same trunk. 

 A large proportion of the specimens were covered on the side 

 on which they lay in the field by an incrustation of lime. This 

 completely obscured the structure and it was necessary to re- 

 move it. This was the case with many of the Black Hills cy- 

 cads, but it presented no serious difficulty beyond the labor and 

 expense of placing the trunks in a vat of hydrochloric acid 

 and leaving them there until the lime was removed, the pure 

 silica of those trunks being wholly unaffected by the process. 

 But, as already remarked, the Jurassic trunks, although mainly 

 silicified, contain calcareous matter, and the acid unavoidably 

 etches the surface somewhat. If this had been all it would 

 have been a comparatively small matter. The worst diffi- 

 culty arises from the fact that the oxidation of the speci- 

 mens turns the parts affected by the acid black or dull brown, 

 and thereby more or less obscures the markings of the surface 

 on which the different organs normally have a different shade 

 of color, which brings them out distinctly. After the acid 

 bath, although the lime is removed and the surface little eaten 



