391 



of the earliest paleozoic formations, but between this and the coal 

 we have as yet been unable to intercalate any one of the vast suc- 

 cession of formations which in the full geological series occupies 

 a place between them. 



The original rock from which the lingula-pebbles were derived, 

 w'hether it shall be brought to light in the neighborhood or may 

 have been buried seaward by an ancient submergence, will most 

 probably connect itself closely in time with the period of the 

 Braintree fossil. But we may hope that further research, aided 

 by the local observation of such zealous inquirers as Mr. Easton, 

 will enable us to supply for this region many other missing rec- 

 ords of the paleozoic ages. 



As regards the age of the conglomerate rock above referred to. 

 Prof. Rogers remarked that, while it was undoubtedly a part of 

 the Carboniferous series, he did not think that its position in the 

 group had as yet been satisfactorily determined. In some locali- 

 ties it was seen overlying sandstones referable to this series, and 

 could not therefore be regarded as the general floor-rock of these 

 deposits, although probably occupying a low position among 

 them. 



Prof. Rogers also made the following communication 

 on the causes which gave rise to the generally elon- 

 gated form and parallel arrangement of the pebbles. 



Referring to the characters of the conglomerate as presented at 

 Purgatory and other places in the vicinity of Newport, and indeed 

 generally throughout its outcrop, he commented on the hypothesis 

 by which it has lately been proposed to explain the elongated 

 form and parallel arrangement of the pebbles in the massive 

 strata of the rock. He described the steep and alternating dips of 

 these thick beds of conglomerate at and near Purgatory, as made 

 apparent by the occasional layers of interposed sandstone, and 

 pointed out the general parallelism there and elsewhere of the 

 flat sides of the pebbles to the planes of deposition, as well as the 

 prevailing uniformity of direction of their longer axes. 



He urged that such an arrangement of the pebbles corresponds 

 precisely with the eifects of wave and current action on water- 

 worn and partially water-borne fragments during their accumula- 



