CLASS IX. ORDER IV. 117 



STROMBUS, (dinner-horn,) aniraal a limax ; 

 shell univalve, spiral ; the lip of the aperture often 

 much dilated ; expanding, and produced into a 

 groove leaning to the left. 



MUREX, (thorn-shell,) animal limax ; shell ine- 

 quivalve, spiral, rough, with membranaceous su- 

 tures ; aperture oval, ending in an entire, straight 

 or slightly ascending ('anal. 



TROCHUS, (top-shell,) animal limax : shell uni* 

 valve, spiral, more or less conic ; aperture some- 

 what angular or rounded, the upper side trans- 

 verse and contracted ; pillar placed obliquely. 



TURBO, (periwinkle, stair-case,) animal limax ; 

 shell univalve, spiral, solid ; aperture contracted, 

 orbicular, entire. 



HELIX, (snail,) animal iimax ; shell univalve, 

 spiral, subdiaphanous, brittle ; aperture contract- 

 ed, semilunar or roundish. In dry and wet soil 

 and water. 



NERITA, (sea-snail,) animal limax ; shell uni- 

 valve, spiral, gibbose, flattish at bottom ; aperture 

 semiorbicular or semilunar ; pillar-lip transverse* 

 ly truncate, flatish. 



HALYOTIS, (sea-ear,) animal limax ; shell uni- 

 valve, dilated ? ear-form, with a longitudinal row 

 of orifices along the surface ; spire lateral and 

 nearly concealed. 



PATELLA, (limpet,) animal limax; shell uni- 

 valve, subconic, shaped like a basin ; without 

 spire. 



TEREDO, (ship-worm,) animal aterebella, with 

 two calcareous hemispherical valves cut off before, 

 and two lanceolate ones ; shell tapering, flexuose 

 ami capable of penetrating wood. 



