654 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



the Bellefonte section may correlate with this division, but their respect- 

 ive faunas are too distinct to lend confidence to the suggested correlation. 



Overlying the preceding division, with a strong chance of a slight gap 

 in the succession, is a fourth bed with a known thickness of 375 feet. 

 This consists of a rapidly alternating series of pure dove limestone, 

 nearly pure gray limestones, and other gray limestones that are rather 

 highly magnesian. Occasioned beds or streaks of fine limestone con- 

 glomerate were observed. The lower 75 feet of this division are limited 

 above by a fossiliferous ledge containing some peculiar sandy chert. 

 Among the fossils are Syntrophia lateralis, Maclurea sordida, and 

 species of Liospira and Orthoceras. The upper 300 feet seem to be un- 

 fossiliferous. 



The fifth recognizable horizon comprises about 200 feet of thin-bedded 

 argillaceous and pure limestone, many of the beds weathering so as to 

 appear riddled with worm borings. Numerous fossils were collected from 

 this division, which is distinguished especially by Maclurea oceanaf, 

 Ophileta? disjuncta, 8olenospira priscaf, Hormotoma gracilens, Turri- 

 toma acreaf, Lophospira gregariaf, TrochoUtes internestriatus , and 

 Cyrtocerina mercuriusf. 



Finally, there is a sixth division, 400 feet or more in thickness, con- 

 sisting, like the fourth division, of interbedded pure and magnesian 

 limestone, all fine-grained and of light shades of gray. Small calcite 

 geodes are common in the lower half or two-thirds, and assist materially 

 in recognizing the bed. Many of the layers are finely laminar, and only 

 those highly magnesian can be called thick-bedded. Near the top are 

 sandy cherts, and above these limestone and dolomite conglomerates; 

 finally, hard, dense, and white chert and also a granular, quartzose 

 variety. Secondar}^ silicification of these cherts often produces a form 

 resembling cauliflower that is rather generally met with about this 

 horizon. AX one place (just north of Greencastle) large quartz pebbles 

 were associated with this peculiar form of chert. The pebbles occurred in 

 a position leaving no doubt that they formed a part of a thin con- 

 glomerate at the base of the overlying lower Stones Eiver limestone. 

 More commonly, probably, the secondarily silicified cherts, including 

 the "cauliflower" variety, mark the same boundary. 



In seeking to correlate the divisions of this Cumberland Valley Beek- 

 mantown section with the divisions of the formations in the Champlain 

 Valley the criteria afforded by lithology suggest at once that the inter- 

 val between the middle of the uppermost member and thence down to 

 the lower half of the third from the top (fourth from the base) corre- 



