Genus LIVONA, Gray Shell top-shaped, heavy, large, with deep umbilicus; whorls rounded; aperture roundish; outer lip sharp-edged; operculum concave outside, thin, smooth, chestnut inside, with olive green muscle scar; body fringed with numerous cirrhi.
The West Indian Top Shell (Livona pica, Linn.) is found in Charlotte Harbor, West Florida, but not in such abundance as farther south. It is a popular sea food in the West Indies and in Central America. The shell itself has some commercial value; it is sometimes four inches high, oftener smaller; when cleaned and polished it shows a beautiful greenish pearly ground with strong black wavy markings. It lives in great numbers on the rocks and coral reefs, near shore, where it may be seen through the limpid water crawling along, waving two long tentacles ahead and a fringe of cirrhi almost as long on each side of the foot. When the surprised tourist sees one of these large top shells climbing a tree (a very common sight in the islands) he may be sure that the mollusk is dead and its vacated shell is inhabited by a hermit crab.
Genus CHLOROSTOMA, Swains.
Shell conical, solid, base of columella toothed, aperture oblique, outer lip smooth within. A large genus, chiefly of Pacific coast species. It is fairly represented in the West Indies.
The Black Top Shell (C. funebrale, A. Ads.) is found in the greatest abundance upon rocks on the California coast. It has a heavy black shell, with distinct swelling of the body whorl below the suture. The apex is blunt, the umbilicus closed; the aperture is lined with greenish pearl; there is a white nodule at the base of the columella. The shell is an inch in height and width.
The Brown Top Shell (C. brunneum, Phil.), also a Californian species, is a clumsy brown thimble in form, about an inch long, with markings of white on the lips and a greenish pearly lining. It lives upon kelp and rocks.
215 The Top Shells and Dolphin Shells The Snake-skin Top Shell (C. pellis-serpentis, Wood) is well named. The heavy, solid shell is 1 I to 2 inches in diameter, a little higher than broad. Its crowded coils are separated by linear sutures, and finely marked with dark patches in intricate patterns on yellow or pink ground colour. The aperture is lined
with pearl; the columella bears a heavy tubercle in the middle, and a small tooth where it joins the thin lip of the aperture.
Habitat.— Gulf of California to Panama.
Genus NORRISIA, Bayle Shell large, round, umbilicated, solid, smooth; spire depressed, conical; whorls few, rapidly enlarging; aperture quadrangular; outer lip sinuous, thin edged; columella sinuous. An isolated genus of one species.
This species is abundant about San Diego, where it is often seen in tide pools, with the strawberry-red body extended, crawl ing on seaweed. Shells are picked up on the beaches after violent storms. It measures one to two inches in altitude, and about two inches in diameter.
Habitat.— Southern California.
Genus CALLIOSTOMA, Swains.
Shell pyramidal, with beautiful colouring and sculpturing; base flattened. A large genus of unusually beautiful shells.
The Ringed (C. annulatum,Martyn) is a specimen people are always interested in collecting. It is abundant in many places along our Pacific coast. Its shell is fragile, and can only be collected in fine weather, and then by going out in a boat and gathering the seaweed to which these delicate creatures cling.
216 The Top Shells and Dolphin Shells In bad weather they sink to the bottom. Fragments are picked up on the beach, but rarely a perfect shell. The whorls are yellowish, ornamented with raised brown dots in parallel rows; the depressions between the whorls and the area about the axis are shaded with purple. The exterior is almost as beautiful as the pearly lining. Height, I inch.