A 



374 DARTON — GREEN POND, N. J., TO SKUNNEMUNK MT., N. Y. 



ately fine-grained, slabb}^ sandstone. It has been quarried to some ex- 

 tent northwest of Monroe for use in flagging, but the quahty of the flags 

 is not very satisfactory. Among the upper members there are scattered 

 conglomerate streaks, of which the most prominent is a twelve-foot bed 

 in a prominent spur on the eastern side of the mountain near the line of 

 section III, plate 17. The upper beds are massive and more or less 

 quartzitic, and it is these which merge into the Skunnemunk conglom- 

 erate. At Clinton falls, west of Newfoundland, these massive upper beds 

 are finely exposed, underlying the red slates. They are there and at 

 many other points much broken and' gashed with veins of quartz. As 

 Bell vale mountain consists largely of these flags, it is proposed to desig- 

 nate them the Bellvale flags. 



The occurrence of the plant remains has been referred to a number 

 of times in preceding pages, for they have afi'orded most important evi- 

 dence as to the age of the formation. 



They comprise the following species : Lepidodendron gasjnanum, Daw- 

 son ; Psilophyton princeps, Dawson ; Calamites transitionis, Goeppert, and 

 some others less definitely identified. 



Professor D. S. Martin was the original discoverer of these remains, 

 which he found in an opening for coal on the southwest slope of Skunne- 

 munk mountain at a point about a mile and a half due north of Monroe 

 station. Smock found additional remains in the old flag quarries near 

 by, where plant fragments are abundant. I have also found fragments 

 at Woodbury falls, on the opposite side of the mountain, and at Clinton 

 falls, west of Newfoundland. 



Prosser* has recently reviewed the occurrences of these remains, 

 obtained new supplies, and discussed their age. The conclusion at which 

 he has arrived is that the plants represent a Middle Devonian horizon, 

 but that precise correlation is not practicable. 



Monroe Shales. — The shale series underlying the Bellvale flags extends 

 around the lower slopes of Skunnemunk mountain, down the valley east 

 of Bellvale and Bearfort mountains, and over a wide area in the low 

 region north of Bowling Green mountain. They are known to occupy 

 the valley southeast of Milton for a number of miles, but their southern 

 termination is not yet definitely ascertained. Their greatest thickness is 

 in the valley and slopes south of Greenwood lake, where it amounts to 

 about 900 feet. On the southeast side of Skunnemunk mountain their 

 thickness is greatly reduced, apparently by gradation into more arena- 

 ceous beds. At Monroe and about the northern end of the mountain 

 they have a thickness of about 200 feet. The most extensive exposures 



* Notes on the Geology of Skunnemunk Mountain, Orange County, New York. N.Y.Acad. 

 Science, Trans., vol. 11, pp. 132-151. 



