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NATURAL HISTORY. [EAST. ZOOL. 
various species, which were most common in the district; 
the true Tyrian dye was most probably derived from 
Mur ex trun cuius. 
The family of Strombidoe (Case 1, 2) are peculiar for 
having a very compressed foot, which only allows them to 
leap and not to walk; their eyes are placed on the end of 
a large thick elongated peduncle, having the slender ten¬ 
tacles arising out of the middle of their hinder sides, and 
the shell is peculiar for having a deep sinus placed on the 
side near the canal over the head of the animal, when it 
is expanded. These animals, when they arrive at their 
full size, expand the edge of the mantle in a remarkable 
degree, which causes the shell of the adult animal to be 
very different from that of the young. This expansion only 
takes place once in their lives, and not at repeated and 
stated periods, as in the Murices , &c. Their operculum 
is narrow and claw-like, the apex being produced beyond 
the point of its attachment, as it enlarges, by new layers 
below. 
All the other Zoophagous Gasteropodes have a broad ex¬ 
panded foot, by which they glide on and attach themselves 
to marine bodies; their eyes are sessile, or placed on a 
very short tubercle near the base, or on the tentacles. 
The family of Muricidce (Case 3) have a more or less 
elongated straight syphon, and the shell has a straight 
tubular canal for its protection; the animal, at certain 
periods of its growth, expands the edge of its mantle, and, 
during this time, deposits appendages on the edge of the 
shell for their protection; these expansions of the mantle 
are then gradually withdrawn, and the portion of shell 
which the animal forms between this time and the next 
development of the appendages, is of the common shape: 
y but the expansions produced for their protection are left on 
the surface of the shell, forming variously shaped bands 
across the whorls, which have been called varices , from 
some of them looking like dilated veins; these varices , 
and the spines upon them, being formed on the expanded 
appendages of the mantle, exactly correspond to them in 
form, and afford good characters for the determination of 
the groups and species. In some of these animals the 
periodical expansions of the mantle are round, forming a 
convex simple granular varix on the shell, and the inner lip 
