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generally more or less lunar. Operculum sometimes testaceous, 

 generally homy, spiral. 



The comparatively recent discovery that the soft parts of Natica are 

 similar to those of Sigaretm, required that these genera, which in 

 Lamarck's time were arranged at some distance from each other in the 

 system, should be brought into more immediate relationship. By mala- 

 cologists, indifferent to the characters of the shell, the Natica have been 

 removed to the Sigaretm family ; but conchologists, unwilling to lose 

 sight of their obvious and long-acknowledged affinity in this respect with 

 the Nerites, have caused the Sigareti to be removed to this family. It was 

 by the Trench navigators, MM. Quoy and Gaimard, during the voyage of 

 the ' Astrolabe/ that the animal portion of Natica was first fully observed, 

 though figured a century before by Adanson. Differing essentially from 

 that of Nerita, it proved to be of very much larger dimensious in pro- 

 portion to the size of the shell, distinguished by a broad mantle-like ex- 

 pansion of the foot, and characterized by a more or less thickened circular 

 ridge, holding the shell, and sometimes almost concealing it from view. 

 The Natica has, moreover, a retractile proboscis, which the Nerite has 

 not, and it is of more predaceous habits. The lobe which carries the 

 operculum is also largely developed and reflected over the shell. The 

 animal of Sigaretm is of similar structure ; and looking only to the dis- 

 tinctive features of organization of the soft parts, there is little family re- 

 lationship between it and the Nerites. 



The shells of Natica are not particularly variable in form. They are 

 nearly all of the same peculiar semiglobose, lunar-apertured plan of con- 

 volution, which is characteristic of the Nerites, more largely umbilicated, 

 but having the umbilicus sometimes filled up with callous enamel, and 

 sometimes partially filled with a peculiar spiral columnar callosity. Little, 

 however, as this variation is, the Natica have been divided into seven 

 genera: — Natica proper (N canrena), Zunatia, Lamarck (N. mouilifera), 

 Neverita, Risso (N. albumen), Ampullina, Lamarck (N fiuctuatd), Ruma, 

 Chemnitz (N Maura), Mamma, Klein (N mamilla), and Naticina, Gray 

 (N. papilla). The chief conchological distinction between the genera 

 Nerita and Natica is, that whilst the Nerites are mostly strongly grooved 

 and otherwise sculptured, and richly painted, the Natica are smooth and 

 polished, as is almost invariably the case with shells more or less en- 

 veloped by the soft parts of the animal, and are painted, generally with 

 light colours. 



The Natica live mostly in sandy and muddy beaches, at about low- 

 water mark, and are strictly carnivorous.* 



* Speaking of a large species, N. heros, inhabiting the shores of Massachusetts, Dr. Gould 

 says, in his history of the Invertebrata of that State : — "This, in common with other species 

 of Natica, is very voracious, and plays a conspicuous part iu devouring the dead lish and other 



