NATICID^. 205 



they liide iinder the surface and bvirrow after bivalves. Range, 

 from low-water to 90 fathoms. The colored markings of the 

 shells are ver}^ indestructible, being frequently preserved on 

 fossils. 



STiGMAULAX, Morch. Whorls cancellated or sillonated ; umbil- 

 icus with spiral funiculum. Operculum with calcareous outer 

 layer. N. cancellata, Lam. (Ixiii, 43). 



LUNATiA, Gray. (Euspira, Agass., in part. Grlobularia, Swn.") 

 Shell usually sombre-colored, covered with a dark, thin epider- 

 mis ; not so thick as the t^qoical group ; umbilicus open, without 

 funiculum. Operculum corneous. Inhabit usually cold or tem- 

 perate rather than tropical seas. N. heros, Say (Ixiii, 44). 



NEVERiTA, Risso. (Naticaria, H. and A. Adams.) Shell 

 depressed, orbicular, spire conical or flattened ; columella partly 

 filled by a tongue-shaped callous process (funiculum) fi'om the 

 columella. Operculum horny. Animal capable of entire retrac- 

 tion within the shell. Inhabits mostly temperate seas. N. 

 duplicata, Say (Ixiii, 45). 



ANOMPHALA, Jouas. (Cemiua, Gray. Bulbus, Brown.) 

 Globular, imperforate, the columella with heavy callous deposit. 

 The animal is bulky, and unable to retract itself entirely into its 

 shell. Operculum, if present, quite rudimentary. N.fiuctuata, 

 SoAvb. (Ixiii, 46). 



AMPULLiNA, Lam. (Globularia, H. and A. Adams. Ampul- 

 linopsis, Conr. Euspira, Agass., in part.) Umbilicus narrow 

 (rimate), lined by a thin callus. Operculum with calcareous 

 layer. N. Sigaretina, Lam. (Ixiv, 66). 



MAMiLLA, Schum., 1817. (Ruma, H. and A. Adams. Nati- 

 caria, Swn.) Shell oval-conic, rather thin, with pointed spire ; 

 whorls fasciated ; mouth oblong, inner lip narrow, reflected, 

 usually brown or black ; umbilicus not funiculated. Oper- 

 culum cartilaginous, oblong, narrower than the aperture. 

 Animal capable of retraction within its shell. N. maura, Lam. 

 (Ixiii, 47). 



MAMMA, Klein. (Polinices, Montf. JSTaticella, Guild.) Shell 

 oval or suboval, solid, smooth, spire short, sharp; aperture 

 semicircular, inner lip oblique, callous, the callus extending into 

 the umbilicus. Operculum corneous ; animal retractile. N. 

 straminea, Recluz (Ixiii, 48). The shell of Mamma is usuallj^ 

 white, sometimes colored, but not banded or spotted. 



AMAUKA, Moller. (Acrybia, H. and A. Adams. Ptychostoma, 

 Laube. ) Shell oval, smooth, imperforate, spire elevated, aperture 

 oblong, columella short, simple. Operculum corneous, thin. The 

 animal has a small, compact foot, without posterior lobe, anterior 

 lobe profoundly sinuous, eyes at the internal base of the lobe. 

 A boreal group, comprising a few living species. Fossil ; Jurassic, 

 Cretaceous, Tertiary. N. Candida, Moller (Ixiii, 46). 



