208 BULLETIN OF THE NEW YORK STATE MUSEUM 



when the mass resembles the roe of a fish ; crinoidal, made 

 up of the stems of fossil crinoids, also are in use, and which 

 are descriptive of texture. The state of aggregation of the 

 constituent particles varies greatly, and the stone is hard 

 and compact, almost like chert, or Is loosely held together 

 and crumbles on slight pressure, or again It is dull and 

 earthy as In chalk. 



The crystalline, granular limestones, which are susceptible 

 of a fine polish, and which are adapted to decorative work, 

 are classed as marbles. Inasmuch as the distinction Is In 

 part based upon the use. It is not sharply defined and scien- 

 tific. Generally the term is restricted to those limestones 

 In which the sediments have been altered and so metamor- 

 phosed as to have a more or less crystalline texture. There 

 Is however some confusion in the use of the terms, and the 

 same stone is known as marble and limestone, e. g., the 

 Lockport limestone or marble ; the limestone and coral- 

 shell marble of Becraft's mountain, near Hudson ; the 

 Lepanto marble or limestone near Plattsburgh, and others. 



The fosslllferous limestones are made up of the remains 

 of organisms w^hich have grown In situ, as for example, the 

 coralline beds in the Helderberg and Niagara limestones, 

 or have been deposited as marine sediments. In the case 

 of the latter the fossils are more or less comminuted and 

 held In a calcareous matrix. Generally the fossil portions 

 of the mass are crystalline. The Onondaga gray limestone 

 from near Syracuse, and the Lockport encrinltal limestone 

 are good examples. 



The fossil remains are less prominent and scarcely visible 

 In some of the common blue limestones, as In the lower 

 beds of Calclferous and in some of the Helderberg series. 

 These rocks are compact, homogeneous and apparently 

 uncrystalline and unfosslllferous. They are usually more 

 siliceous or argillaceous, that Is, they contain quartz or 

 clay, the latter often In seams rudely parallel with the bed- 

 ding planes. On weathering, the difference In composition 



