60 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [354] 
bivalve shells by means of the small flinty teeth on its lingual ribbon, 
which acts like a rasp, and having thus made an opening it inserts its 
proboscis and sucks out the contents. All sorts of burrowing bivalves 
in this way fall victims to this and the following species, nor do they 
confine themselves to bivalves, for they will also drill any unfortunate 
gastropods that they may happen to meet, not even sparing their own 
young. . 
A variety of this species (var. triseriata, Plate XXIII, figs. 135, 136) 
has three revolving rows of chestnut or purplish spots, and has been 
regarded by most writers as a distinct species, and sometimes as the 
young; but both the plain and spotted shells occur of all sizes, from the 
the youngest to the oldest, and they are nearly always found together. 
In some cases, however, a shell that has the spots well defined until 
half grown, afterwards loses its spots and becomes perfectly plain, show. 
ing that the difference is only a variation in the color, but each style 
varies considerably in form. 
Another allied shell, growing nearly as large and generally much 
more abundant, except on the outer beaches, is the Neverita duplicata, 
(Plate XXIII, fig. 130.) This species has the same habits as the pre- 
ceding and in this region they are often found together; but this is a 
more southern species, extending to the Gulf of Mexico and even to 
Texas, but it is not very common north of Cape Cod and does not 
extend to the eastern coast of Maine and Bay of Fundy. 
The curious egg-cases of this and the last species are often met with 
on the sandy and muddy flats at low-water. They consist of a broad, 
thin ribbon of sand, coiled up into a circle and shaped something like a 
saucer, but without a bottom; the ribbon is composed of innumerable 
little cells, each containing one or more eggs and surrounded with 
grains of fine sand cemented together by mucus. The cells can easily 
be seen by holding one of these ribbons up to the light and looking 
through it. The peculiar form of these egg-masses is due to the fact 
that they are molded into shape by being pressed against the body of the 
shell when they are being extruded, and while they are still soft and 
gelatinous; they thus take the form and spiral curvature of that part 
of the shell, and when laid in the sand the fine grains at once adhere 
to and become imbedded in the tenacious mucus, which soon hardens. 
The Tritia trivittata (Plate X XI, fig. 112) is also frequently found on 
sandy shores and flats. When left by the tide it creeps along the sur- 
face of the sand, leaving long crooked trails, and sometimes burrows be- 
neath the surface, and when burrowing it moves with the aperture down- 
ward and the spire pointing obliquely upward, but when at rest in its 
burrow it reverses its position and rests with the spire downward and 
the aperture toward the surface. 
The Llyanassa obsoleta (Plate XXI, fig. 113) is also generally to be 
found in considerable numbers creeping over the flats, and making trails 
