98 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OP MARYLAND 



the greater part, occur mainly in reef-like masses. These reefs are of 

 slightly different material than the enclosing rock, lenticular in form, 

 and seldom exceed two feet in maximum thickness. Straight and coiled 

 cephalopods are the most abundant fossils seen in cross-sections of these 

 reefs, but Maclurites and Ophil eta-like gastropods are not uncommon. 



Most of the beds of the upper Stonehenge resemble the Conococheague 

 limestone so closely in their development of sandy laminated strata with 

 numerous beds of edgewise conglomerate that in areas of faulted or 

 intricately folded strata the distinction between the two formations is 

 made with difficulty. The absence of chert in the weathered Stonehenge 

 limestone contrasting with its frequent occurrence in the Conococheague 

 is perhaps the best of the physical means of separation. It will be 

 observed also that in the upper Stonehenge the sandy laminae are more 

 undulating and interwoven than in the laminated beds of the Conoco- 

 cheague in which commonly they form relatively parallel bands. The 

 presence of shells of cephalopods and gastropods in the Stonehenge also 

 serves to distinguish this member from the Conococheague which has 

 never yielded any molluscan fossils. In areas where the sequence is 

 normal the boundary between the two formations is readily determinate 

 by the criteria given. Desirable and conclusive corroboration may be 

 secured by establishing the lower Beekmantown sequence of ( 1 ) the lower 

 Stonehenge composed of pure dove-colored to gray strata containing beds 

 of a minute limestone conglomerate; (2) dark impure limestone with 

 undulating siliceous laminae followed by (3) relatively pure limestone 

 consisting largely of pinkish marbles. 



All the hills within the city of Hagerstown and its vicinity are formed 

 of the upper Stonehenge limestone, .and as the quarries for building stone 

 in the early days were located on these hills, it follows that many of the 

 older buildings in Hagerstown are of this limestone. The stone is not 

 only easily quarried and dressed, but as it whitens in weathering and the 

 edgewise conglomerate and wavy laminae become distinctly visible, it has 

 also a handsome and unique appearance. Several of the churches are 

 constructed of Stonehenge limestone and its value and beauty as building 

 rock may be seen particularly in St. John's Episcopal Church on West 

 Antietam Street, and the Presbyterian Church at the corner of Wash- 



