GENERA OF SHELLS. 87 



plaited or transversely wrinkled. Lip usually 

 dentated. 



Distinguished from buccinum by the longitudinal 

 direction and narrow form of its aperture, by the right 

 lip being toothed, by the flattening of the pillar lip, 

 which generally projects considerably to the left side, 

 and by the abrupt reflection of the base of the canal 

 towards the back of the shell. The spire is but little 

 elevated and often interrupted by oblique, keel-shaped 

 varices. 



C. tuberosa, Madagascarensis, cornuta. 



DlV. II. AN OBLIQUE NOTCH INCLINING BACK- 

 WARDS. 



RICINULA. Shell ovate, generally tubercu- 

 lous or spinous without. Aperture oblong, 

 presenting inferiorly a semicanal, turning back- 

 wards, terminated by an oblique notch ; une- 

 qually toothed on the columella and internal 

 surface of the lip, generally contracting the 

 aperture. 



The ricinulaB are generally small shells : the spire 

 often low and covered with tubercles or spinous points 

 like the fruit of the ricinus. The aperture is generally 

 tinged with purple or violet. 



R. horrida, miticula, clathrata, arachnoides, digitata, as- 

 pera, morus, mutica, pisolina. 



PURPURA. Shell oval, sometimes smooth, 

 sometimes tuberculous or angular. Aperture 

 dilated, terminating inferiorly in an oblique, 



