GASTROPODA 537 



Family 1. NATICIDAE. 



Shell usually globose or flattened, with a short spire; aperture round 

 or lunar; lip sharp; umbilicus open, or closed by a callus; operculum 

 usually corneous; foot very large and capable of being swollen by the 

 taking in of sea water into open spaces and reflected back over the shell 

 so as almost to cover it; tentacles small, lanceolate, wide apart, united 

 by a veil; eggs deposited in a "sand collar," a thin collar-shaped lamella 

 formed by agglutinating grains of sand together by means of nmcous: 

 several hundred species. 



Key to the genera of Naticidae here described : 



ffi Shell globose 1. Natica 



02 Shell flattened with a very large aperture. 



\ Shell ear-shaped 2. Sigaretus 



6j Shell trumpet-shaped 3. Velutina 



1. Natica Lamarck. Shell smooth and regular, gray or brownish 

 in color, with about 5 whorls; eyes wanting; umbilicus usually more or 

 less closed by a large callus: over 200 species; predacious animals, liv- 

 ing in the sand, where they burrow after bivalves; they envelop their 

 prey in the foot and penetrate its shell, drilling a hole with the radula ; 

 they also devour dead fish; about 20 species on the Atlantic coast. 



Key to the species of Natica here described : 

 Oi Shell over 25 mm. long. 



&i Umbilicus wide and deep N. heros 



5, Umbilicus nearly closed by a brown callus N. DUPLICATA 



ff2 Shell 15 mm. or less long. 



&i Umbilicus wide and deep N. IMMACULATA 



&2 Umbilicus more or less covered by a white callus. 



Ci Shell 8 mm. or less long N. pusilla 



€2 Shell over 10 mm. long. 



di Shell with minute revolving lines N. grcenlandica 



da Shell without revolving lines N. clausa 



N. {Polynices Montfort) heros Say (Fig. 

 831). Shell large and moderately thick; whorls 

 5, convex; umbilicus large and deep; length 9 /|i 

 cm.; diameter 8 cm.; shell ash color, streaked t-^'^V;^ 

 with chestnut: Virginia to Labrador; from low- . ^^^fj^^W 

 water mark to 238 fathoms; common. ^&^:!0.'' 



N. (PoZ2/»**ces Montfort) duplicata Say. Shell w^s?*!^^ 



solid, whorls 5, flattened above ; spire low ; color Fig. g^i 



1 X J- X 11 ii Natica heros (YerrUl). 



ashy gray, tending towards brown on the upper 1, umbilicus ; 2, aperture. 



side, chestnut brown within; callus very large, 



chestnut brown in color, almost filling the umbilicus; length and 



diameter 5V2 cm.: Massachusetts Bay to Mexico; common in shallow 



water. 



