GEOLOGY AND PALEONTOLOGY OP THE SCHOHARIE VALLEY 365 



degrade — to wear down to the condition of grade — as in a river 



dental plates — plates or brackets supporting the hinge teeth in the brach- 



iopod shell 

 dichotomous — branching in a bifurcating or forking manner 

 dip — the relation which an inclined stratum bears to a horizontal plain 

 discoidal — disklike 

 disintegrate — break up by the combine^ action of chemical and mechanical 



forces 

 dissepiment — small discontinuous connecting plates between the septa of 



corals 

 dodecahedron — the crystal form in which 12 equal diamond-shaped faces 



occur — example, garnet 

 dodecahedron — pentagonal — the crj-stal form (hemi-tetrahexahedron) in 



which 12 equal faces, each of the form of a regular pentagon occur. 



Characteristic of pyrite. 

 dorsal — pertaining to the back or dorsum 

 dynamic — pertaining to or involving forces 



ear — the anterior division of the hinge of pelecypods 

 elevation, median — see fold 

 emargination — marginal notch 



estuarine — appertaining to an estuary or the mouth of a river 

 exogastric — in coiled cephalopod shells with the ventral sinus on the 

 arched external side 



fault — displacement of strata with reference to each other on opposite 



sides of a fracture line 

 fauna — the sum total of animal life of a given region, a given formation 



or a given time 

 ferruginous^ — iron-bearing 



fissile — splitting into thin, more or less papery sheets 

 fluorite — the mineral form of calcium fluorid 

 fold — a bend in the strata 

 fossils — remains of animals and plants or direct evidence of their presence 



preserved in the rocks of the earth 

 fragmental rocks — same as clastic rocks 

 furrows, glabellar — the transverse depressions on the central portion or 



glabella of the trilobite head 

 furrows, lateral — side depressions bounding the glabella of the trilobite 



head 

 furrows, occipital — basal depression separating glabella from last ring of 



head of trilobite (occipital ring) 



gastropods — a class of invertebrate mollusks, typically with a coiled shell 



as in the snails 

 genal angles — the angles of the cheeks or lateral angles of the head of 



trilobites 

 genal spines^ — the lateral or cheek spines of the trilobite head 

 geodes — hollow concretions lined with crystals or massive mineral matter 

 gibbous — thick, bulging 

 glabella — the central portion of the head of trilobites 



