32 TERMS USED 



drawn out to a considerable length, as Trochus Telescopium, 



and Turbo Terebra. 

 Teres is tapering, but not spirally turned, as Dentalium En- 



talis. 

 Tvbidosus is a tube in different forms, as in the genus Serpula. 

 Rectus is straight, as Nautilus Raj)hamstrum and Orthocera. 

 Angulatus, angular, is generally applied to shells not spiral, as 



Patella saccharina. 

 Orbiculatus is nearly like half a globe, the shell not spiral, as 



Patella equestris. 

 Ocalis is a flat oval shell, as Patella crepidula and forni- 



cata. 

 Auriformis is ear-shaped, as in the genus Haliotis. 

 Convexus is wlien the shell is but little convex, or between 



sub-globosus and planus, as in Trochus Magus and Helix 



virgata ; Helix Lapicida is convex on both sides. 

 Depresses is nearly like convexus, bvit flatter, as Troclms umbi- 



licatus and Helix ericetorum. 

 Planus is flat, as Helix Vortex and contorta. 



OF THE PARTS OF UNIVALVE SHELLS. 



The principal parts of Univalves are the spire, the aperture 

 or mouth, the lips, and the operculum. 

 Spira, the spire, is that part of the shell where the turns or 



whorls are seen in a spiral form. 

 Apertura, the aperture or mouth, whence the animal in part 



comes out or retires at will. 



