KINGSTOWN SERIES OF WESTERN BRISTOL NECK. 343 



ward, since the more northern exposures on the island show that the sand- 

 stones and conglomerates are overlain by the dark-bluish shale, with only 

 a small interval of unknown rock. The most ready interpretation of this 

 fact is to suppose that the lower part of the Aquidneck shales is often coaly, 

 the thickness of this coaly section, however, being greatly variable. 



western Bristol Neck. — Bluish and greenish Aquidneck shales form the main 

 mass of the Carboniferous rocks on Bristol Neck. Underlying them on 

 the southwest is a thick bed of sandstone, amounting to perhaps 50 feet 

 About 225 feet beneath this bed occurs more sandstone, of dark color, con- 

 taining coaly matter, and perhaps 150 feet beneath this level is coaly shale 

 with fern-leaf and Annularia impressions. If the eastward dip of 20° is 

 maintained, the conglomerate exposed at two localities above the main sand- 

 stone bed first mentioned lies about 250 feet above the latter. A short 

 distance above the conglomerate begin the greenish and dark-blue shales 

 of the Aquidneck series. The order of succession on the western side of 

 Bristol Neck is, therefore: coaly shale, gray or darker sandstone, bluish 

 sandstone, conglomerate with large pebbles, greenish and dark-blue shales. 

 If the great shale series of Bristol Neck be correlated with the shales of 

 Prudence Island and southern Conanicut, the underlying rocks may repre- 

 sent the upper part of the Kingstown series. Certain facts suggest a 

 relationship with at least the Prudence Island section. Pebbles containing 

 oboli are found in the conglomerate on the west side of Prudence 

 Island. While the pebbles of the conglomerate on the west side of Bristol 

 Neck are of much larger size, their lithological character agrees very well 

 with that of the Prudence Island pebbles, and oboli will no doubt be 

 eventually found there also. There is a considerable section of sandstone 

 on the west side of Bi-istol Neck. It is not interbedded with the con- 

 glomerate, but is found beneath it. The coaly shale on Bristol Neck, as 

 w r ell as that on Prudence Island, contains plants, but the coaly shale on 

 Bristol Neck occurs, not at the base of the greenish and dark-blue shales, 

 but below the sandstones and conglomerates of that field. As a matter of 

 fact, however, these latter belong very high in the Kingstown series, and 

 strict parallelism of strata could hardly be expected at so great a dis- 

 tance as that from Prudence Park to western Bristol Neck, in a geological 

 field where lithological changes along the strike are frequent. Only a 

 general accordance could be demanded. For this reason the coaly shales, 



