390 THE CHICAGO ACADEMY OF SCIENCES. 
Torsion. A twisting around. 
Tortuous. Twisted or winding. 
Torpid. Half unconscious or asleep, as a snail during hibernation. 
Translucent. Not quite transparent; light is seen through the thin 
edges of the object. 
Transparent. Objects may be seen through the substance. 
Transverse. Referring to the form of a sheil when it is wider than 
high. 
Tricuspidate. Having three cusps. 
Trifid. Having three branches, 
Trigonal. Having three angles. 
Trilobate. Having three lobes. 
Tripartite. Divided into three parts, as the foot of some snails. 
Truncate. Having the end cut off squarely, as some Unios (pl. xiv, 
fig. 1). 
Tuberculate. Covered with tubercles or rounded knobs (pl. xiv, fig. 1). 
Turbinate. Having the form of a top. 
Turriculated. Having the form of a tower. 
Turreted. Having the form of a tower. 
Umbilicated. Having an opening in the base of the shell (pl. xxviii, 
fig. 21). 
Undulated. Having undulations or waves, as the surface of some 
Unios (pl. xxil, figs. 1, 2). 
Univalve. Having the shell composed of a single piece, as a snail. 
Varicose. Swollen or enlarged. 
Vascular. Containing or made up of blood vessels. 
Vermiform. Formed like a worm. 
Ventral. The lower border or side. 
Ventricose. Swollen or inflated on the ventral side. 
Vibratile. Moving from side to side. 
Vitreous. Resembling glass, as some snails. 
3S Male. The astronomical sign for the planet Mars. 
@ Female. The astronomical sign for the planet Venus. 
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