354 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



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 aud 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 nearl^^ as large and generally' much 

 more abundant, except on the outer beaches, is the Neverita duplicaia^ 

 (Plate XXIII, fig. 130.) This species has the same habits as the pre- 

 ceding aud 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 aud 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 comi^osed 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 aud become imbedded in the tenacious mucus, which soon hardens. 



The Tritia trivittata (Plate XXI, 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 Ihjanassa ohsoJcta (Plate XXI, fig. 113) is also generally to be 

 found in considerable numbers creeping over the Hats, and making trails 



