64 The Ottawa Naturalist [Aug.-Sept. 



that it is sometimes a good deal easier to discover the fossili- 

 ferous zones in the Beekmantown than the glomerates 

 subjacent to them. The study of intraformational glomerates 

 includes a careful examination of the phenoclasts and cement 

 as well as the structure and field relations of the strata above 

 and below the zone in question. The examination of the 

 texture, shape and composition of the phenoclasts and cement 

 is mainly petrographic in its nature, and upon it will largely 

 depend the plausibility of the students' views as to origin. 



Certain liberties have been taken with Walcott's original defi- 

 nition of intraformational conglomerates. This was deemed neces 

 sary for two reasons: first, because some of the types discussed 

 by Walcott are not typically conglomeratic (in the geological 

 sense) ; second, because the term is such a useful and necessary 

 one in stratigraphy that it should be applicable to an important 

 group of elastics intimately associated with the history of the 

 Paleozoic and Mesozoic seas. Whether or not it will ultimately 

 be deemed advisable to group such rocks as tectibreccias, bio- 

 glomerates and edgewise conglomerates under the term intra- 

 formational is open for discussion. The attempt has been made 

 to list and classify certain clearly, as well as obscurely, defined 

 examples of limestones, w r ith the hope that this systematic study 

 may help in reaching the ultimate goal the history and origin 

 of the calcareous terrains of the world. 



DESCRIPTION OF FIGURES. 



Figure 1. Diagramatic sketch of a supposed bioglomerate 

 from the lower Beekmantown limestone at Bellefonte, Penna. 

 The large phenoclast on the right hand side of the figure shows 

 structure which may be organic in origin. Most of the pheno- 

 clasts present peculiar outlines not at all similar to the outlines 

 of the pebbles in an ordinary conglomerate. The small dots 

 are supposed to represent agal-like organisms' which have worked 

 their way into the soft limy material and broken it up into 

 the characteristic shapes shown in the diagram. The pheno- 

 clasts are fine grained, and sometimes contain fragments of 

 small fossils. Most of the fossils, however, are found in the 

 more granular ground mass. 



Figure 2. This figure is illustrative of an actual specimen 

 of mud-cracked limestone found in one of the quarries at Belle- 

 fonte, and illustrates on a smaller scale the phenomena exhibited 

 on the east wall along the strike of the quarries from Bellefonte 

 to Tyrone, Pennsylvania. The shaded lines on the surface, 

 traversed by the two parallel calcite veins, represent mud- 

 cracks. Viewed in section the structure is that of a typical 

 stratified glomerate. The figure is supposed to illustrate the 



