75 



MONOGRAPH OF THE GENUS 



NATICA. 



Testa plerumque solida ^lobosa, saspissime umbilicata ; 

 spira brevi, frequenter vix exserta, anfractibus paucis ; um- 

 bilico aut amplo, aperto, aut callo spiral! partim impleto, 

 aut callo columellari tecto ; apertura jslus minusve semi- 

 lunari. Operculum sa?pissime corneuru tenue paucispirale, 

 •interdum testaceum. — The Naticse' are generally globose and 

 solid. The most solid and compact are those which, like 

 N. canrena, have a spiral callus inside the umbilicus, and a 

 large proportion of these have an operculum with a shelly 

 outer surface. Others, like N. didyma and its allies, have 

 the callus of the columella spread into a more or less rounded 

 pad, covering a large part or the whole of the umbilicus, and 

 have a thin horny operculum. A few species are quite thin 

 and simple, and without any umbilicus. The only division 

 that could he made would be between those species with a 

 shelly, and those with a horny operculum, but these are not 

 always known, and do not correspond with other divisional 

 characters. The shells of Naticse are mostly smooth, some 

 even polished, being more or less wrapped up in the opercu- 

 ligerous lobes. The divisions of the genus in the work of 

 the late Messrs. Adams are : 



1. Natica. With spiral callus in umbilicus, and shelly 

 operculum. Ex. N. canrena. 



2. LuNATiA. With simple umbilicus, or none. Operc. 

 generally horny. Ex. L. catena. 



3. Neocrita. Flat-spired, with lobed callus. Operc. 

 horny. Ex. N. olla. 



