NATICIDA. 207 
Tycuonta, de Koninck, 1881. 
Distr.— T. Omaliana, de Kon. Carboniferous; Belgium. 
Shell somewhat depressed, globular, smooth; spire short, 
obtuse, sutures shallow; last whorl very large; mouth semicir- 
cular, outer lip sharp, inner lip somewhat callous; an umbilical 
fissure. 
Sigaretus, Lam. 
Syn.—Catinus (Klein', H. and A. Adams. Lupia, Conr. 
Stomatia, Hill. Raynevallia, Ponzi. 
Distr.—90 recent sp. United States, West Indies, China, 
Peru. Fossil, 10 sp. Eocene—. 8S. neritoideus, Linn. (1xiii, 
52). 
Shell ear-shaped, with minute spire and very large aperture, 
externally with revolving striae, color usually white, with some- 
times a thin corneous epidermis. Operculum minute, horny, 
subspiral. Animal with large mantle partly or entirely covering 
the shell, anterior foot-lobe enormously developed. 
They live on muddy sand-flats; im their habits they are 
sluggish and slow-moving, and very timid; when crawling they 
constantly explore the surrounding surface with the produced 
fore-lobe of the foot, which is also used in burrowing. 
SIGARETUs, Lam. (typical). Shell orbicular, conoidal or convex ; 
mouth rounded; umbilicus open or covered by a reflection of the 
inner lip; spire short, oblique. 
NATICINA, Gray. (Lacunaria, Conr.) Shell oval-oblong, thin, 
ventricose ; spire sharp; inner lip straight, thin anteriorly, with 
amedian callus; umbilicus open or partly covered. 8S. papilla, 
Gmel. (1xiii, 53). 
CRYPTOSTOMA, Blainy. Shell ear-shaped, flattened; spire short, 
depressed ; mouth very large, oblique; no umbilicus. 8S. halio- 
toides, Linn. (Ixiii, 54). 
Ve uTina, Fleming. 
Etym.— Velutinus, velvety (from vellus, a fleece). 
Syn.—(?) Catinella, Stache. 
Distr.—4 sp. Boreal Seas, Europe and America. Fossil. 
Triassic, Cretaceous, Pliocene—. V. capuloidea, Blainv. (1xiii, 
55). V. laevigata, Linn. (xiii, 56). 
Shell thin, with a velvety epidermis ; spire small, sutures well- 
impressed ; aperture very large, rounded ; peristome continuous, 
thin. No operculum. 
Animal with a large oblong foot; margin of the mantle 
developed all around, and more or less reflected over the shell ; 
head broad; tentacles subulate, blunt, far apart, with eyes on 
prominences at their outer bases. 
The Velutinas, although resembling the pulmoniferous genus 
Otina, are strictly marine, being met with sometimes far out at 
