10 INTRODUCTION 
ensconced under projecting surfaces. Most species are more 
plentiful at the lowest-water mark, and many are found only at 
this point and below. 
SANDY SHORES 
On sandy shores the greater part of the inhabitants live under 
the surface. Many give evidence of their presence by the open 
mouths of their burrows, and some distinctly point out these 
places by piles of sand or mud in coils at the opening. Some 
tubicolous worms have their tubes projecting above the surface. 
The tubes of Diopatra are hung with bits of shells, seaweeds, and 
other foreign matter. Some mollusks announce themselves by 
spurting jets of water or sending bubbles of air from the sand. 
The majority of the underground species, however, give no sign 
of their presence on the surface, and must be found by digging. 
Many of them go deep into the sand, and in searching for worms 
the digger must be quick and expert, or he will lose entirely or 
cut in two many of the most beautiful ones, which retreat quickly 
and to the extremity of their holes at the least alarm. One can 
be a rambler on the sandy beach for a long time without being 
aware of the many beautiful objects which inhabit the subsurface 
of the sand. The curious crab Hippa will disappear so quickly 
into the sand that one is hardly sure he has really seen it. The 
vast number of worms will surprise any one who searches for 
them by their variety, their beautiful color, and their interesting 
shapes. Here again a glass is requisite to appreciate the delicacy 
and beauty of their locomotive organs, their branchie, and s0 on. 
The most common of the gasteropod mollusks on sandy shores 
are Nassa obsoleta, Nassa trivittata, and Polynices (Lunatia) heros. 
The last are detected by the little mounds of sand which they 
push before them as they plow their way just below the surface. 
On more southern beaches, Fulgur, Strombus, and Pyrula are the 
common varieties. Olivella, Oliva, and Dona., also inhabitants of 
sandy beaches, will quickly disappear when uncovered by the 
waves, being rapid burrowers. Most of the many dead shells on 
the beach will be found to be pierced with a round hole, which is 
