124 CLASS ACEPHALA. 
articulated and ciliate. ‘They should be remarked on account 
of the analogy which they establish with the ee Such 
is the Teredo palmulatus, Lam. 
FISTULANA, Brug. 
Separated from teredo: the external tube is entirely closed at 
its larger end, and is more or less like a bottle or club. The 
fistulane are sometimes found in submerged fragments of 
wood, or in fruits that had sunk in the water, sometimes 
simply enveloped in sand. The animal, like that of a teredo, 
has two small valves and as many palettes. Recent specimens 
are only obtained from the Indian Ocean, but they are found 
fossil in Europe. (Teredo clava, Gm., &c.) We should ap- 
proximate to them the 
GASTROCHENA, Spengler, 
In which the shells are deprived of teeth, and their edges being 
wide apart, anteriorly, leave a large oblique opening, opposite 
to which there is a small hole in the mantle for the passage of 
the foot. The double tube, which can be retracted com- 
pletely within the shell, is susceptible of being greatly elon- 
gated. It appears that they are certainly furnished with a 
calcareous tube. 
In some of them, as in the mytili, the summits are at the 
anterior angle, (Pholas hians); in others they are placed near 
the middle. 
They inhabit the interior of madrepores, which they per- 
forate. Two genera of acephala, furnished with tubes like 
the teredines, have been detected among fossils, but the first 
of them, the 
TEREDINA, Lam., 
Has a little spoon-shaped impression on the inside of each of 
its valves, and a small, free, shield-shaped piece on the hinge. 
(Teredina personata, Lam.) In the second, 
