128 THE CAMBRIAN. [bul£.81. 



These same limestones in Pennsylvania, which belong to the Lower Taconic series 

 of Emmons, have also afforded an undescribed species of Lingula. 1 



In reporting on the Paleozoic rocks of Lehigh and Northampton 

 Counties Mr. Fred. Prime, jr., states that the very lowest beds of the 

 Potsdam sandstone are actually pudding-stones, containing pebbles the 

 size of a man's fist and larger, and fragments of red, unaltered ortho- 

 clase, The upper beds are composed of a hard, compact quartzite con- 

 taining greater or less quantities of feldspar nodules. The sandstone 

 often, as elsewhere, contains Scolithus. 2 He gives the geographic dis- 

 tribution of the sandstone as found about the South Mountain in the 

 two counties mentioned. Of the upper Primal slates he says : 



Next above the Potsdam sand stone occur hydromica slates, which Kogers has called 

 the Upper Primal slates, but which really form a portion of the No. II limestone, 

 and gradually pass into this. They overlie the Potsdam conformably and are far 

 more persistent in their occurrence. 3 



In the limestone he found specimens of the genus Mouocrateriou in 

 Lehigh County, specimens of Lingula, and a single specimen of an 

 orthoceratite. 4 In the vicinity of Allen town and Bethlehem the sand- 

 stone is about 25 feet thick. The contact between the gneiss and the 

 sandstoneis distinctly seen about 2 miles from Allentown, on the Lehigh 

 Valley Railroad track. (Prof. Prime's paper was also printed in the 

 American Journal of Science, under the following title : " On the Dis- 

 covery of Lower Silurian Fossils in Limestone Associated with Hydro- 

 mica Slates, and on other points in the Geology of Lehigh and North- 

 ampton counties, Eastern Pennsylvania.") 5 



The species of Monocraterion was described and illustrated by Prof. 

 Prime in 1878. 6 It is stated to be from the Siluro-Cambrian limestone. 



Prof. Rogers referred nearly all of the strata of the South Mountain, 

 southwest of the Susquehanna River, to the Primal series. He says: 



In its geological constitution this tract is without much variety, for it contain 

 scarcely auy rocks except those of the Primal series. 7 



He describes the ridges as composed of the Primal white sandstone 

 and the intervening valleys and plateaus of the Primal upper slate. 

 These strata are represented as very much disturbed and extensively 

 metamorphosed. This view is not accepted by Dr. Persifor Frazer, who 

 says that in his report of 1875 (Second Geological Survey of Pennsyl- 

 vania, CC) it is clearly shown, both in the text and in the graphic 

 illustrations, that the Potsdam or Primal formation of Rogers is want- 

 ing over all that country with the exception, perhaps, of scattered 

 patches on the northwestern flank of the South Mountain chain. 8 



1 On the history of the crystalline stratified rocks. Am. Assoc. Proc, vol. 25, 187(3, p. 208. 



2 On the Paleozoic rocks of Lehigh and Northampton Counties, Pennsylvania. Am. Phil. Soc, Proc, 

 vol. 17, 1878, pp. 248, 249. 



3 0p.cit.,p.249. 4 0p. cit.,p.251. 



5 Am. Jour. Sci., 3d ser., vol. 15, 1878, pp. 261-269. 

 «2d Geol. Sur., Penn., DD, 1878, pp. 79-80. 



7 The Geology of Pennsylvania. Philadelphia, 1858, vol. 1, p. 203. 



8 Frazer, Persifor, jr. (On the relations of the South Mountain rocks in Pennsylvania.) Am. Inst. 

 Mining Eng., Trans., vol. 7, 1879, p. 336. 



