OSCILLATORY CHARACTER OF CONTINENTAL SEAS 323 



limestone 207 feet thick, is followed by a 40-foot bed of argillaceous gray 

 limestone and calcareous- shale containing the second appearance of 

 Echinosphcerites, with many brachiopods and other fossils characterizing 

 the Christiania fauna. The faunal association is so closely like that 

 found 2 to 6 miles south of Chambersburg that the contemporaneity of 

 the two occurrences seems unquestionable. 



Basal member of the Martinsburg formation. — Overlying the Chris- 

 tiania bed the Strasburg section shows about 300 feet of thin-bedded, very 

 argillaceous, light gray limestone and calcareous shale, referred to the 

 Martinsburg and passing at the top apparently gradually into darker true 

 shales. No fossils were seen in this impure limestone except in the rela- 

 tively shaly part that lies 10 to 30 feet above the base. Several layers 

 here were filled with Corynoides cf. gracilis and calycularis, Climaco- 

 graptus spinifer, Leptoholus insignis, Schizocrania filosa, Dalmanella 

 testudinaria? and Caryocaris sp. nov. This association compares rather 

 well with the fauna at Van Schaick Island, New York, listed by Ruede- 

 mann,^2 and probably is the same as one found by Weller at Branchville, 

 New Jersey.^^ Possibly this 300-foot bed is equivalent to the 200-foot 

 bed of heavy-bedded limestone and shale found at the top of the Cham- 

 ])ersburg limestone at Greencastle, Pennsylvania, but, in the writer^s 

 opinion, it is a subsequent deposit. At both localities, it is true, the next 

 succeeding shale contains Triarthrus hecki, Trinucleus concentric us, and 

 Caryocaris, with other less diagnostic fossils. Also that these same Crus- 

 tacea occur in a similar dark shale just over 120 feet of argillaceous lime- 

 stone and shale at Martinsburg and again at Chambersburg, only 'here it 

 is found directly over the Christiania bed. But the respective faunas of 

 the heavy-bedded limestone at Greencastle and the 300-foot bed of argil- 

 laceous limestone at Strasburg are essentially different. The 12 species 

 found in the former are all either the same or closely allied to species 

 found in the Christiania bed or lower, while those observed in the Cory- 

 noides bed are all distinct and more suggestive of Trenton and so-called 

 TJtica species. These facts indicate ( 1 ) a withdrawal of the waters of the 

 basin at the close of the Christiania bed, except in a local depression in 

 the vicinity of Greencastle, in which the remnant was retained long 

 enough to accumulate massive calcareous sediments to a maximum thick- 

 ness of about 200 feet; (2) a gradual resubmergence of the basin with 

 northward diminution of calcareo-argillaceous deposits that, as stated, 

 diminish from 300 feet at Strasburg to 120 feet at Martinsburg and are 



^' R. Ruedemann : New York State Museum. Bull. No. 42, 1901, p. 524. 

 " Stuart Weller : New Jersey Geological Survey. Kept, on Paleontology, vol. 3, 1903. 

 p. 52. 



