PART II. 



ROTELLIN-ffi. 



353 



cemented and incorporated with the calcareous sub- 

 stance of the shell ; the under part of the body-whorl 

 flattened or concave, umbilicate. 



O. Solaris. Mart. 173. f. 1700, 1701. 

 Indicus. Ib. 172. f. 1697, 1698. 



SUB-FAM. ROTELLINJE. 



Substance perlaceous ; shell depressed, smooth, and 

 highly polished ; mouth thin ; umbilicus closed.* 



CHRYSOSTOMA/S'W. Shell turbinate; 

 the whorls few and convex; 

 aperture effuse, round ; inner 

 lip thickened, just over and 

 almost concealing the umbilicus. 

 Nicobaricus. Mart. 182. f. 1822-1825. (fig, 109.) 



ROTELLA Lam. Shell flattened, nearly discoid, polished ; 

 inner lip very thick, and spreading over half of the 

 under surface ; aperture small, angulated j operculum 

 horny, (fig. 109- f, 9-) 



R. lineotata Lam. Mart. 166. f. 1601. e,f, g. 



THELIDOMUS Sw. (fig. 113.) Turbi- 

 nate, sub-trochiform ; umbilicus large,, 

 open ; the whole shell entirely com- 

 posed of grains of sand. 



Braziliensis Sw. (Jiff. 113.) 



SUB-FAM. PLEUROTOMARLE. 



Trochiform ; the aperture with a slit or 

 fissure. Fossil only. 



PLEUROTOMARIA Defrance. Spire more or less elevated. 

 Being only found in an imperfect or fossil state, nothing 

 has been determined as to the umbilicus,, substance! 

 operculum, &c. 



P. reticulata. Sow. Gen. t. 1. 



* These have probably no operculum, and Rotella may be an internal 

 shell. 



