374 ; MARINE INVERTEBRATES 
aperture. The Cerithude include a large number of genera, 
mostly tropical in distribution. Their shells are usually highly 
ornamented in various schemes of sculpture, but they lack beauty 
in color. The animal is provided with a siphon, ag is indicated 
by the anterior canal of the shell. The operculum is corneous, 
with a nearly central nucleus. 
Genus Cerithium 
C. floridanum. A very common species on the west coast of Florida, 
also sparingly found at Hatteras. It has eight or ten whorls, a grad- 
ually tapering spire, and a sharp apex; the aperture is oblong, with a 
deeply cut anterior canal projected to the left and backward (when the 
specimen is held apex up, with the aperture toward the observer). The 
sculpture is elaborate, consisting of many rows of revolving ribs, and 
close to the suture there are circling rows of nodes. There is a curious 
hump just to the left of the aperture, which is quite characteristic of the 
genus. The color is whitish-gray ; the length one and a quarter to one 
and a half inches. Station, shallow water in lagoons and sheltered 
spots. (Plate LXIX.) ‘i 
C.muscarum. Another Floridian species, somewhat smaller than 
the last (one inch in length). It has heavy, prominent, transverse ribs 
crossed by circling rows of chestnut: spots, one heavy revolving rib 
around the base; eight or nine whorls; a high-tapering spire; and a 
sharp apex. The aperture is oblong, with the anterior canal projecting 
to the left. The columella is arched; the color shining gray to very 
light purplish. This very pretty little shell may be gathered literally by 
the shovelfu] all along the west Florida coast in sheltered spots, on sandy 
and shallow bottoms. (Plate LXIX.) 
C. minimum. A still smaller Floridian shell, with jet-black aperture 
and anterior canal projecting horizontally to the left. The seulpture- 
plan is of revolving ribs and a series of white granules just below the 
sutures. Its station is the same as that of the last. Often the bottom 
of a lagoon will seem to be literally paved with these somber-hued 
ae avs From Tampa Bay to Charlotte Harbor they are very 
abundant. 
GeneRA Bittium, Triforis 
These are allied genera, having numerous species upon our 
coasts, but the shells are so small that the inexpert collector is 
not likely to notice them. Hosts of these minute, turreted, de- 
cussated, blackish shells are to be found on the wiry grasses of 
salt-marshes. They are also found on alge at low-water mark. 
In Triforis the whorls turn to the left. Range from Cape Cod to 
South Carolina. 
