364 



NEW YORK STATE MUSEUM 



checking — breaking up into small checkerlike square fragments character- 

 istic of some mudrocks 

 chert — the amorphous or irregular form of silica occurring in limestones 

 (flint) 



clastic rocks — rocks composed of fragments of older rocks — e. g. sand- 

 stones, conglomerates etc. 



cleavage — (mineral) the property of splitting along certain planes deter- 

 mined by the crystalline structure 

 (rock) splitting into parallel sheets as in the case of roofing slates 



coastal plain — the level plain composed of horizontal or gently sloping 

 strata of clastic material fronting the coast and generally representing 

 a strip of recently emerged sea bottom 



col — the low saddle connecting two hills or peaks 



conchoidal — with a curved surface marked by lines resembling the lines on 

 a clam shell ; the type of fracture found in glassy rocks or shown in 

 thick glass 



concretion — a rock mass of varying form resulting from the segregation 

 of mineral matter from all portions of the parent rock in favorable 

 spots within this parent rock. The form, composition and mode of 

 formation varies greatly 



conformation — having a parallel position with reference to each other, as 

 two strata or beds 



conglomerate — a clastic rock composed of waterworn pebbles embedded in 



a matrix of varying composition 

 conseciuent stream — the type of stream resulting from the flow of water 



down a constructional slope or land surface 

 coralline limestone — limestone composed of or containing many corals or 



coral-like remains, specifically the Cobleskill limestone 

 corallite — one of the members or tubes of a compound head of coral, as in 



Favosites 



correlation — determination of the equivalency or relative age of geologic 



formations in separated localities 

 costae — ribs on the surface of shells or other organisms 

 coquina — a rock composed entirely of shells, generally but little broken 

 crenulations — fine ridges or toothlike markings 



crinoids — a class of marine invertebrates of the division Echinoderniata. 



consisting typically of a body or calyx composed of more or less regular 



scries of plates, set generally on a jointed stalk or stem, and bearing 



arms. A " sea lily " 

 cross-bedding — the variable angle of the layers or beds within a stratum 



of rock produced by strong currents, specially in rivers 

 cuesta — a topographic form resulting from the normal erosion of coastal 



plain strata of varying hardness, and comprising a steep escarpment 



or inface facing the old land and separated from it by a parallel valley 



and a gently sloping upper surface formed by a resistant stratum. 



See illustration in body of text, figure 210 

 cycle of erosion— the interval during which a land surface newly uplifted 



either as plain or mountain is worn down to the level of the sea (base 



level) 



cystoid — a class of organisms related to the crinoids, but with the calyx 

 composed of irregular plates 



