THE SHELL-FISH OF THE COAST. 29 
— 
along the beach you cannot fail to have noticed 
peculiar gray, collar-like bodies scattered about, 
some of them forming almost complete circles, and 
measuring six inches or more across. Examined, 
these collars are seen to be made up of minute sand- 
particles glued together, and if held up to the light 
exhibit an almost innumerable number of translu- 
cent spots. These spots correspond to the positions 
of egg-cases which are distributed throughout the 
mass in a single layer, and in quincunx order. 
The whole is, in fact, the egg-ribbon or ‘ nidus’ of 
the Natica—a construction unlike that of any other 
mollusk. Just how it is made still remains a mys- 
tery, but it appears that as it is extruded in the 
form of a viscous mass it is immediately moulded 
over the external face of the shell, which gives to 
it its peculiar spiral curve. The coating of mucus 
then draws to it the sand-particles which line it on 
either side. Two forms of this ribbon occur on 
our coast—one, a simple collar with a constricted 
neck, the other, sharply ruffled on its border. The 
former belongs to Natica heros, the latter to N. du- 
plicata. The crowded little pouches, each of about 
the size of a spangle, which are frequently found 
on one side of the collar, are the egg-capsules of 
the dog-whelk (Nassa). 
Of the several other species of marine snails 
occurring on our coast a few are found only at rare 
intervals, and not unlikely their shells have been 
merely washed hither without the animal itself 
living along the immediate coast-border. Among 
these are the auger-shell ( Zerebra dislocata), a com- 
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