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NEW YORK STATE MUSEUM 



suture — the line made by the junction of the septum with the shell in 

 the Cephalopoda. Visible when the cavities of the shell are filled with 

 rock matter and the shell removed, the common condition seen in 

 fossils. Also the line of junction between the coils or whorls of a 

 gastropod shell. 



talus — the accumulation of rock debris at the foot of a cliff 

 telson — the spine at the end of the tail of crustaceans 

 tenuous — drawn out finely 



terebratuloid — related to or resembling the brachiopod genus Terebratula 

 texture — the grain of rocks 



till — the unassorted material left by the melting ice sheet of the glacial 

 period. It is generally full of boulders and contains much clay and 

 rock flour 



torticone — a twisted cone as in snail shells (gastropods) or certain cepha- 

 lopoda (Trochoceras) 



transgression — encroachment on. as the sea advancing over the land which 

 it submerges 



trilobate — three lobed 



trilobite — a class of Crustacea, longitudinally divisible into three parts or 

 lobes and having a head or cephalon with a central glabella, com- 

 pound eyes and lateral or free cheeks separated from the rest of the 

 head by the facial sutures: a body or thorax divided into a number 

 of rings and a pygidium or abdomen consisting of a single grooved 

 piece. The class is confined to the Paleozoic rocks 



tufa, calcareous — a deposit of porous lime carbonate formed by certain 

 springs or streams 



tumid — swollen 



umbilicus — the basal cavity in the axis of circling of gastropod and cepha- 

 lopod shells 



umbonal — pertaining to the beak or umbo of bivalve shells 

 unconformity — discordant relation of strata 



unconformity, stratigraphic — an unconformity marked by absence of 

 certain intermediate formations without discordance of strata (dis- 

 co n form ity ) 



unconformity, structural — a true unconformity with discordance of strata 

 The first scries is folded and eroded before the second is deposited [see 

 text] 



venter — underside of the body. In coiled cephalopod sliells it is mostly the 



outside of the coil 

 ventral — pertaining to the underside of the body 

 ventricose — bulging 

 vermes — the class of worms 

 vitreous luster — (he luster of fjlass 



waterlime — limestone Which on burning will form natural cement 

 whorls — fbe coils of a gastropod or coiled cephalopod shell 

 wing — in certain pelecypods flic posterior or larger portion of the hinge 

 region; fbe anterior or smaller portion is the ear 



