NATICA. 



Plate I. 



Genus NATICA, Adcmson. 



Tenia globosa vd neritoidea, interdiim aperti bijlntii, ^pird 

 irevi, scspisslme rix exsertu, aiifractibiis pa/tcia, iimhi- 

 licum amplum formantUms, mine caUosUute dciiad hn- 

 pleto, nunc callodtate colmnnari qjiraliter iidrantc, 

 apertiird plerumqiie plus miwu^ lunari. Operculum 

 interdum, testaceim, sapissinie corneum, spirale. 

 Shell globose or neritoid, sometimes openly inflated, spive 

 short, very often scarcely exserted, whorls few, form- 

 ing a large umbilicus, which is sometimes filled with 

 a dense callosity, sometimes with a columnar callosity 

 entering spirally, aperture generally more or less 

 lunar. Operculum sometimes testaceous, generally 

 horny, spiral. 

 The comparatively recent discovery that the soft parts 

 of Natica are similar to tliose of Si(jaretm, requii-ed that 

 these genera, which in Lamarck's time wore arranged at 

 some distance from each other in the system, should be 

 brought into more immediate relationship. By malacolo- 

 gists, indifferent to the characters of the shell, the Natica 

 have been removed to the Siffaivli ; but conchologists, un- 

 willing to lose sight of their obvious and long-acknow- 

 ledged affinity in this respect with the Nerites, have caused 

 the Sigareii to be removed to the Neritacea. It was by 

 the French navigators, MM. Quoy and Gaimard, during 

 the voyage of the ' Astrolabe,' that the animal portion of 

 Natica was first fully observed, though figm-ed a century 

 before by Adanson. Dift'ering essentially from that of 

 Nerita, it proved to be of very much larger dimensions 

 in proportion to the size of the shell, distinguished by a 

 broad mantle-like expansion 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 predaeeous habits. The 

 lobe which carries the operculum is also largely developed 

 and reflected over the shell. The animal of Sigaretius is 

 of similar structure ; and looking alone to its distinctive 

 features of organization, there is little family relationship 

 between it and the typical soft parts of Neritacea. 



The shells of Natica are not particularly variable in 

 form. They are nearly all of the same peculiar semiglo- 

 bose, lunar-apertured plan of convolution, which is cha- 

 racteristic of the Nerites, mostly largely umbilicated, but 

 having the umbilicus sometimes filled up with callous 



enamel, and sometimes partially filled with a peeidiar 

 spiral columnar callosity. Little, however, as this varia- 

 tion is, the Natica have been divided into seven genera : — 

 Natica proper {N. canrena), Liouitin, Lamarck (iV. moidli- 

 fera), Neverita, Kisso {N. alhiimeii), Ampullina, Lamarck 

 {N.Jliwtuata), Ruma, Chemnitz {N. Maura), Mamma, Klein 

 (iV. mamiiiiUa), and Naticiiia, Gray (iV. 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 ease with shells more or less enveloped by the soft 

 parts of the animal, and painted, generally with light co- 

 lours. 



The Nulira' live mostly in sandy and muddy beaches, 

 at about low-water mark, and are strictly caruivorous. 

 Speaking of a large species, N. /leros, inhabiting the 

 shores of Massachusetts, Dr. Gould says, in his history of 

 the Invcrtebrata of that State; — "This, in common with 

 other species of Natica, is very voracious, and plays a 

 conspicuous part in devouring the dead fish and other 

 animals which are thrown up by the tide. Many of the 

 shells thrown upon the shore are found to be perforated 

 with a small round hole : this is done principally by the 

 difi'erent species of Natica. They have the power of per- 

 forating shells, it is generally supposed, by discharging an 

 acid which decomposes the shell, and through the aper- 

 ture they extract the juices, and destroy the lives of the 

 otherwise secure inhabitants. Their foot is very large, so 

 as to completely envelope the objects on which they prey. 

 In moving, they burrow in the sand, so as to be almost 

 entirely concealed by it, and their place is generally indi- 

 cated by a small heap of sand. The singular nidus in 

 which the animal of Natica deposits its eggs has been an 

 object of much curiosity and speculation. It is a mass of 

 sand glued together into the shape of a broad bowl, open 

 at the bottom, and broken at one side. Its thickness is 

 about that of an orange-peel, easily bent without breaking 

 when damp, and when held up to the light will be found 

 to be filled with little cells, arranged in quincunx order. 

 Each of these cells contains a gelatinous egg, having a 

 yellow nucleus, which is the embryo shell." 



Species 1. (Mus. Cuming.) 

 Natic.\ Ca.aipeachiensis.. N,iI. Icsld umliiticatd, de 



April, 185 



