4 NATTCID^E. 



Animal with small tentacles, which are lanceolate, wide apart, 

 connected by a veil ; eyes absent, or placed under the skin, 

 behind the tentacles ; foot much produced in front, where it is 

 furnished with a fold (propodium) covering the head and anterior 

 margin of the shell ; operculigerous lobe very ample, partially 

 enveloping the shell ; mantle enclosed. Jaws corneous, waved or 

 tessellated, subtrigonal (PL 1, fig. 3). Central tooth of the 

 radula trapezoidal, generally tricuspidate, lateral teeth with a 

 central large and smaller cusps, inner marginals simple or bifid, 

 outer marginals simple (PI. 1, figs. 4-6). 



The animals of Naticidrc, characterized by the cephalic disk 

 forming the propodium, are completely retractile within the 

 shell in the typical Natica, but not retractile in Sigaretus and 

 Mamilla. In some species of Neverita, the posterior margin of 

 the propodium forms on the left side a sort of fleshy siphon ; the 

 operculigerous lobe, which encircles the shell sometimes has a 

 sinus on the right side, probably for the introduction of water 

 into the branchial cavity. 



The Natica (PL 7, fig. 43) is an active animal, carnivorous and 

 very predaceous, living in sandy places, where it hides under the 

 surface and burrows for bivalves. These it pierces with its 

 tongue, boring a round hole, generally near the beaks, where 

 the shell of the victim is thinnest. The eyes, hidden by the 

 propodium, and subcutaneous, are generally not perceptible, but 

 can be distinguished in the group Amaura. 



The Nidus (PL 7, figs. 44, 45) is unlike that of any other 

 mollusk in form and composition, being built up largely of 

 the sand of the sea-bottom, agglutinated into a strap, forming 

 part of a circle, and provided on one side with a constriction or 

 rim ; the walls contain the eggs, arranged in quincunx order. 



Subfamily II. Lamellar iinse. 



Shell thin, sigaretiform, more or less internal, generally pauci- 

 spiral, sometimes reduced to a non-spiral auriform lamina; spire 

 short, few-whorled, lateral; aperture oval, entire, large. No 

 operculum. 



The animal (PL 1, figs. 18, 19) has not the cephalic disk of 

 Xatica. The mantle gradually grows over the shell until the 

 hitter becomes, in some of the rcnor:i, completely internal ; eyes 



