PEALE.] 



GEOLOGY SECTION NO. 18. 231 



uess. These sandstones extend from e to g in the illustration. At 

 the point/ there is a small fold. The general dip is to the east- 

 ward, at an angle of from 10° to 20°. The angle is greater on the 

 west side of the fold. The thickness of the sandstones is about 

 903 feet. 



25. Black and greenish-gray sandstones, shales micaceous, 6 feet. 



26. Sandstone, 51 feet. 



27. Blue limestone, very dark, and weathering of a reddish brown color, 



20 feet. 



28. Sandstones, couglomeritic, generally of a gray color, about COO to 



800 feet. 



29. Fine black shales, 6 feet. 



30. Greenish-gray micaceous, sandstone-shale. The mica is silvery and 



especially distinct between the laminae. They become quartzitic 

 above, 34 feet. 



31. Bluish and brownish limestone, with interlamiuated shales, 10 feet. 

 32.* Sandstone, 2 feet. 



33. Limestone, 4 feet. 



34. Fine black argillaceous shales, 9 feet. 



35. Coarse grayish sandstone, 10 feet. 



36. Limestones and shales, 6 feet. 



37. Greenish-gray micaceous sandstones. Toward the top the beds be- 



come very coarse, 15 feet. 



38. Limestones and bluish argillaceous shales with sandstones. The 



upper portion of the bed contains in blue shaly limestones fine 

 specimens of Productus semireticularis, P. nebrascensis, Spirifer 

 opimus^ Productus prattenamts, and a Pleurotomaria,* 57 feet. 



39. Black shaly limestones, in the lower part of which we find the fol- 



lowing fossils, Productus Spirifer, and fragments of Trilohites, 34 

 feet. 



40. Quartzite sandstone laminated and micaceous, 15 feet. 



41. Space covered with the debris of a porphyritic volcanic rock, 5 feet. 



42. Shaly limestone, 3 feet. 



43. Space covered with debris of volcanic rock, limestone, and sand- 



stone, 27 feet. 



44. Porphyritic volcanic rock, about 10 to 20 feet. 



45. Blue laminated limestone, 10 feet. 



46. Quartzitic sandstone, lighter colored and laminated above general 



color, steel gray to brown, 6 feet. 



* Pleukotomaria Taggarti, Meek. 



Shell attaining a large eize, turbinate, very thin, slightly longer than wide; spire 

 depressed, conical, a little shorter than the length of the aperture ; volutions five to 

 five and a half, flattened above to the slope of the spire, last one very prominent and 

 angular around the middle, with the under side slightly convex and eloping inward 

 nearly at right angles to the flattened slope of the upper side above the peripheral 

 angle ; suture merely linear; umbilical region but very slightly excavated and imper- 

 torated ; aperture rather large, subquarate, with height and breadth apparently nearly 

 equal ; spiral band extremely narrow, occupying the peripheral angle of the body 

 volution, and passing around only about its own breadth above the suture on those of 

 the spire ; surface nearly smooth, or showing only obscure lines of growth, with ap- 

 parently me^ly the faintest i)ossible traces of revolving striae. Height about 2,60 

 inches ; breadth about 2.49 inches. 



In size and general appearance this fine species somewhat resembles P. missourierisis, 

 {TrocliHsmiHHOuricnsia, Swallow,) but it maybe at once distinguished by having its body 

 volution below the periphery longer than the height of the spire above ir, instead of 

 flattened, as well as by wanting the distinct revolving lines of that species. The 

 specilic name is given in honor of William K. Taggart, esq., of Dr. JIaydeu's survey, 

 who discovered the tyi^e specimen. 



