































THE HALIOTIS, OR PEARLY EAR-SHELL. 253 
of the sea-water to the respiratory organs, analogous to the 
single vertical and nearly central hole in the shell of Fissu- 
rella. The holes in Haliotis are placed in a row nearly equi- 
distant from centre to centre, upon the left side of the shell, 
parallel with the columellar lip, and being required only in 
that part of the shell which covers the branchial cavity, 
those nearest the apex are closed or grow up as the animal 
advances in growth. The holes furnish a passage for slender 
tentaeular filaments which the animal can protrude at pleas- 
ure; the hole or notch for the passage of the anal siphon is 
situated at the posterior margin of the shell. The animal 
of Haliotis, according to P. P. Carpenter, “has two gills and 
two auricles, instead of one, as in the top-shells.” Its head 
is blunt and terminates in a short muzzle, with two subulate 
tentacles and two stout eye peduncles at their bases. Upon 
the upper extremity of the foot it has a rudimentary opercu- 
ligerous lobe, but no operculum. The foot is very large, 
rounded at the ends and fringed with thread-like tentaculæ, 
Which, when the animal is protruded from the shell, below 
the surface of the water, are gently swayed with a some- 
what vibratory motion. ‘The muscular attachment, instead 
of being horseshoe shaped as in ordinary univalves, is round 
and central, as in the oyster." (Carpenter. ) 
_In adult shells in many of the species, the roughened por- 
tion of the interior indicates the area of the muscular at- 
tachment, while in young specimens the impression of the 
muscle is not shown. 
The Haliotides are sedentary in their habits, as one would 
Suppose, being both vegetarians and conservatives, and 
though capable of locomotion, they move but little and 
quite slowly; their structure, as seen in the powerful mus- 
cular foot, shows it is made for adhesion. They attach 
themselves to the rocks with the greatest tenacity, and E 
have often found it exceedingly difficult to remove them, 
: using a stout trowel, of a shape similar to the kind 
Used by bricklayers. — | 

