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A DICTIONARY OF TERMS. 



Testacea. - 



Tiled. - - ■ 

 Transverse. ■ 



Tricuspidate. 



Trifid. - - - 

 Trilobed. - • 

 Tubercle. 



Turba 



Turn, 



All animals of the class Mollusca, which are 

 covered with a solid roof of carbonate of lime, 

 come under the denomination of Testacea. 



See Imbricated. 



Across. Bands, or stria?, running across a shell, 

 are called transverse. 



A shell armed with three short points. The 

 Anomia tridentata is an example. 



Slit into three. A trifid tooth. 



Having three lobes. 



A protuberance, or knob, raised on the surface 

 of some shells. Several species of the genus 

 Murex, are loaded with tubercles. 



All the whirls, or spires, of a Univalve, taken 

 collectively, are called the turban. The Helix 

 planorbis, has a flat turban ; the Trochus tuber- 

 culatus a short turban, and the Trochus Zizi- 

 phinus a produced turban. 



The turn of a spire, is a single, but complete 

 revolution. In the Nautilus, the last turn of the 

 spire envelopes all the others. 



Umbo. 

 Umbilicus, 



Undulated. 

 Unilocular. 



Univalve. 



Valve. 



U. 



The same as summit. 



A small hole at the bottom of some Univalve 



shells, formed in the thickness of the columella, 



or pillar. 

 Waved. 

 This term is used for Univalves, that have but one 



chamber. The Paper Nautilus, the Cozvries, 



the Olives, &c. are unilocular shells. 

 A division of shells, composed of but one valve, or 



piece. 



V. 

 The testaceous covering of the Mollusca. When 



of a single piece, the shell is called Univalve ; 



when of two pieces, Bivalve ; and when formed 



of more parts than two, Multivalve. 



