124 CONCHOLOGY. 



4. Natica. Thirty-one species. 



A marine shell, formerly classed with the Nerita, but dis- 

 tinguished by being without teeth, and having an umbilicus 

 modified by the callosity. 



Shell smooth, rather thin, and not covered with epider- 

 mis ; the spire evident, though low, umbilicated ; the colu- 

 mellar edge not toothed, more or less callous, modifying the 

 umbilicus ; the right edge thin and not toothed interiorly ; 

 operculum calcareous or horny and smooth, semispiral, with 

 concentric ribs fitting into a slight groove on the columella. 



N. canrena. The Canrena Natica. 



Sub-globular, smooth, umbiHcus deep, bordered anteriorly 

 by a kind of callous column ; spire a little prominent ; ex- 

 terior fawn coloured, with bands and rays of reddish brown ; 

 interior white ; operculum calcareous. 



N. castanea. The chestnut Natica, PI. 21, fig. 6. 

 Species with the umbilicus uncovered, and the operculum 

 horny. 



