NIAGARA FALLS AND VICIXITY 275 



umbilicus — external opening of tlie hollow axis of a loose coiled shell 

 umbo — area about and including the beak in pelecypods and brachiopods 

 unconformity — irregularity in the succession of rock beds indicating an in- 

 tervening period of erosion 



valvular — pertaining to a valve 



varix — row of spines, a ridge or other mark, denoting the former position of 



the lip on the shell of a gastropod (plural varices) 

 vaulted — arched 



ventral — pertaining to the lower side, or venter 

 ventricose — strongly swollen, or bulging 

 vesicular — bearing vesicles, or hollow cavities 

 vestibular area — area surrounding the cell apertures of some bryozoa; often 



depressed 

 viscera — the internal organs of the body 



whorl — single volution of a coiled shell 



wing — posterior larger expansion along the hinge-line of a pelecypod 



zoarium — aggregates of the polypites of a bryozoan colony 



zooecium — the bryozoan cell 



zooid — one of the '' persons " or individuals of a zoarium 



