152 The Lower Devonian Deposits of Maryland 



Keyser. The following section of the Keyser has been measured in the 

 cut:^ 



Helderberg Formation 



Vertical Total 

 Keyser Member thickness vertical 



feet thickness 



Drab, shaly limestone with a bed 1 foot thick in middle of 



unit 2.8 139.2 



Dark blue massive limestone with many calcite seams. Hackle 



teeth at bottom 2.0 137.4 



Dark, compact limestone, containing Meristella prcenuntia 



and Sehuchertella prolifiea ^ (a) 1.5 135.4 



Three heavy beds of compact, dark blue limestone, indis- 

 tinctly banded with fine brown lines. Leperditia altoides abund- 

 ant 4.3 133.9 



Six beds of drab limestone, distinctly banded with fine brown 



lines. Shale parting at top of unit 7.4 129.6 



Single bed of dark limestone, distinctly banded; fracture 



conchoidal 4.2 122.2 



Dark gray limestone with many transverse calcite seams; not 



banded; shale parting above and below 1.9 118.0 



Dark gray limestone; banding indistinct; fracture conchoidal 2.9 116.1 

 Drab limestone, distinctly banded with fine brown lines; 3- 



inch shale parting at base 1.6 113.2 



Thin-bedded drab limestone; distinctly banded 3.1 111.6 



Nodular gray limestone, with Stromatopora 1.4 108.5 



Shale with large nodules 0.8 107.1 



Yellow, argillaceous limestone 1.0 106.3 



Reef of Stromatopora 1.5 105.3 



Irregular shale with large nodules 0.8 103.8 



Drab, banded limestone in moderately thick beds, .i 4.2 103.0 



Yellowish, argillaceous limestone, not distinctly banded. Lep- 



tana rhomboidalis 2.0 98.8 



Massive gray limestone. Stromatopora in upper 3 feet. 



Lower part covered by travertine i. . 7.0 96.8 



Unit almost concealed by residual clay and travertine. Lower 



3 feet nodular, cherty limestone 10.5 89.8 



Massive gray limestone, full of chert, resembling Stroma- 

 topora 3.5 79.3 



Massive, dark nodular limestone; shale parting at top of unit. 

 Uneinulus sp. about 2 feet above base 6.6 75.8 



' Measured by C. K. Swartz, assisted in the field work by J. B. Reeside, Jr., 

 and W. A. Price, Jr. 



' The vertical altitudes of the fossils listed in this section are only approxi- 

 mately known, the section, as described above, differing somewhat from the 

 measurements made by the collector. 



