INTRODUCTION. 23 



23. VOLUTA : Aperture effuse, the pillar plaited. 



24. BUCCINUM: Aperture with a small canal leaning to 



the right. 



25. STROMBUS. Aperture with a small canal leaning to the 



left. 



26. MUREX: Aperture with a small straight canal. 



27. TROCHUS : Aperture contracted, and somewhat trian- 



gular. 



28. TURBO: Aperture contracted and orbicular. , 



29. HELIX : Aperture contracted, lunate on the inner side. 



30. NERITA: Aperture contracted, and semiorbicular. 



31. HALIOTIS: Shell ear-shaped, aperture dilated, with a 



row of orifices along the surface. 



2. WITHOUT A REGULAR SPIRE. 



32. PATELLA: Shell conic, the aperture widened like a 



basin. 



33. DENTALIUM: Shell slender, subulate, open at both ends. 



34. SERPULA : Shell tubular, mostly serpentine, adhering 



to other bodies. 



35. TEREDO: Shell thin, penetrating wood. 



36. SABELLA: Shell composed of agglutinated grains of 



sand, &c. 



