14 GENUSDOLIUM. 



render the aperture of the shell narrower than in the preceding 

 species. I think that the MALEA crassilabris of the same au- 

 thor, described also in the same work, is only a variety of the 

 shell in question. It evidently presents all its characters, ex- 

 cepting some slight distinctions of little importance : it is a little 

 smaller ; the spire is a little more developed, and the right lip 

 thicker. 



DIVISION OF THE TUNS INTO TWO GROUPS. 

 A. Species ivith the right lip always thin and undulated. 



D. perdix, Lam. The partridge tun. 



olearium, Lam. onion-peel tun. 



galea, Lam. fluted tun. 



maculatum, Lam. speckled tun. 



variegatum, Lam. variegated tun, 



B. Species with the right lip more or less widened by the 

 margin, and pretty strongly denticulated. 



D. fasciatum, Lam. The banded tun. 



pomum, Lam. helmet-formed tun. 



latilabre, Nobis. broad lipped tun. 



