GLOSSARY. 



183 



Umbonate, bossed, having a. raised 



knob in the centre 

 Undulated, waved, having a waved 



surface. 

 Ungulate, shaped like a horse's hoof. 

 Unilocular, with a single chamber or 



compartment. 

 Univalve, shells consisting of one 



valve or piece. 

 Volutions, the wreaths or turnings of 



the shells of univalves. 

 Urceolate, swelling in the middle like 



a pitcher. 



spatulated mark in several 



bivalve shells ; formed when the 

 valves are united on the posterior 

 and anterior slopes. 



W. 



Whorl, one of the wreaths or turnings 

 of the spire of univalves. 



Zigzag, having contrary turnings and 



windings. 

 Zoned, surrounded with one or more 



girdles. 



