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ORDER TUBULIBRANCHIATA. 
SEVENTH ORDER OF THE GASTEROPODA. 
TUBULIBRANCHIATA. 
THE tubulibranchiata should be detached from the pectini- 
branchiata, with which they are very closely allied, because 
the shell, which resembles a more or Jess irregularly shaped 
tube, only spiral at the commencement, attaches itself to 
various bodies ; they consequently are deprived of copulatory 
organs, and fecundate themselves. In the 
VERMETUS, Adans., 
We remark a tubular shell, whose whorls, at an early age, still 
form a kind of spire, but afterwards continue in a tube more or 
less irregularly contorted, or bent like the tubes of a serpula. 
This shell usually attaches itself by interlacing with others of 
the same species, or is partly enveloped by lithophytes. The 
animal having no power of locomotion, is deprived of a foot 
properly so called; but the part which in ordinary gasteropoda 
forms the tail, is here turned under it, and extends to beyond 
the head, where its extremity becomes enlarged, and finished 
with a thin operculum. When the animal withdraws into its 
shell, it is this mass which closes the entrance. It is some- 
times seen with various appendages, and in certain species the 
operculum is spiny. ‘The head of the animal is obtuse, and 
has two moderate tentacula, on the external sides of which, 
at the base, are the eyes. The mouth is a vertical orifice, be- 
neath which is a filament on each side, that has all the appear- 
ance of a tentaculum, but belonging in reality to the foot. 
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