MEDINA SANDSTONF. 



^ 



The whole substance and arrangement is angular, and there is some reason to hesitate in 

 assenting to its organic character. It covers large surfaces of the stone ; and there is no evi- 

 dence, on the largest slabs obtained, of any thing like a commencement or termination of the 

 structure. Every branch or reticulation is connected with the stone by the small rootlike fibres, 

 as in the figure ; and surfaces several feet in extent present no deviation from the general 

 character given in this figure. The surfaces thus covered present a most singular and beautiful 

 appearance ; and when in some cases covered by ripplemarks, the interesting character is 

 greatly enhanced. 



Position and locality. This peculiar form is known only in the terminal gray portion of the 

 rock (gray band) at Medina in Orleans county. (State Collection.) 



Pl. III. Figs. 3 & 4. 



Fucoide* auriformis, and f. heternphyllus. Report of the Fourth Geological District of New- 

 York, 1843, p. 47. 



Fig. 4. Surface covered with irregular auriform elevations, single or overlapping each other. 

 These appear like casts of soft material, made in cavities in the rock below. 



Fig. 3 has a still more artificial character, presenting irregularly rugose or striated elevations 

 which have no prevailing or definite shape. 



These forms were described in the Report of the Fourth District as different species of 

 FucoiDES ; but I have not, up to this time, been able to satisfy myself that they are organic. 

 They appear among the many curious cind remarkable markings which cover large surfaces in 

 the Medina sandstone and Clinton group, but which can scarcely be referred to organic remains. 

 A shallow sea, with the proximity of beaches and sudden transitions in the nature of the de- 

 posits, have produced many appearances upon the surface that at first view might be attributed 

 to organic influences, but which are doubtless due to the influence of waves, currents, and 

 perhaps to other dynamical causes. 



The kind of markings in question are found abundantly at Rochester, and also at Medina 

 and other places in Western New- York. {State Collection.) 



387. CHiETETES 



Pl. IV. Fig. 1. 



This species is undistinguishable from the branching forms in the Trenton limestone, and is 

 represented here from the interesting circumstance of occurring in the Medina sandstone at 

 Lockport. 



