182 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
matrix the material is a compact quartzose sandstone, without trace 
of lime and with but enough iron to give it a reddish tinge. More¬ 
over, although similar sandstone is abundantly developed in portions 
of the conglomerate area, it nowhere shows signs of concretionary 
action. 
No other action comes to mind as capable of producing similar 
forms, unless it is assumed that they may be due to jointing. But 
it seems extremely improbable that jointing should produce such 
regular forms. Moreover, the surfaces lack all the characteristic 
features of joints, Woodworth, ’ 96 , pp. 163-188. 
All things considered, the forms are best explained as casts and 
moulds, and may be fairly assumed to be of organic origin. 
Granting this, it is still true that these fossils do not definitely 
