ACEPHALA TESTACEA. 
381 
properly so called, a lamina projecting from one valve into the other, and an internal ligament proceeding 
from that lamina to a corresponding fossa. The cloak is reflected outward upon the hinge, and con- 
j tains one or sometimes two or three supernumerary pieces. The foot issues by the opening at the side 
! of the mouth, which is the widest, and from the opposite end there comes out the two tubes united in 
one, and capable of being extended in every direction. The Pholades inhabit cells which they have 
made, some in the mud, others in rocks, [and others in wood]. They are sought after [in some 
countries] from their agreeable taste. 
Pholas dactyliis, Linn., occurs on our coasts. [The genus Xylophaga of Turton, which burrows in decayed wood, 
is reduced by Deshayes to Pholas.] 
The Teredines {Teredo, Linn.) — 
Have the mantle extended in a tube much longer than the two small rhomboidal valves, and terminated 
by two short tubes, the base of which is furnished on each side with a calcareous and moveable kind 
of operculum or palette. These Acephales, while quite young, penetrate and establish their habitations 
in submerged pieces of wood, such as piles, ship’s bottoms, &c., perforating and destroying them in 
every direction. It is thought that, in order to penetrate as fast as it increases in size, the Teredo 
excavates the w’ood by means of its valves ; but the tubes remain near the opening by which its entrance 
was effected, and through which, by the aid of its palette, it receives water and aliment. The gallery it 
inhabits is lined wdth a calcareous crust which exudes from its body, and which forms a second kind 
of tubular shell for it. It is a noxious and destructive animal in the seaports of Europe. 
The common species (T. navalis, Linn.), which is said to have been introduced from the torrid zone, has more than 
once threatened Holland with ruin, by the destruction of its dikes. It is six inches in length and upwards, and 
has simple palattes. In tropical countries, there are large species with jointed and ciliated palettes, which deserve 
notice for the analogy they establish with the Cirrhopodes. Such is the Teredo pahmdatus, Lam. 
The Fistulana, Brug. — 
Has been distinguished from Teredo, for its external tube is entirely elosed at its larger end, and is more 
or less like a bottle or club. The speeies are sometimes found buried in wood or fruits that have been 
apparently submerged in the water ; sometimes they are simply enveloped in the sand. The animal 
has two small valves and two palettes, as in the Teredo. Recent speeimens are brought from the 
Indian Oeean, but our formations have preserved some fossil speeies. 
Near Fistulana we should place Gastroclicena, Spengler*, whose shells have a toothless hinge, and the margins 
being wide apart in front, leave a large oblique opening, opposite to which there is in the cloak a small opening for 
the passage of the foot. The double tube, which can be concealed entirely within the shell, is capable of great 
elongation. It appears certain that they have a calcareous tube. In some species, the beaks are at the anterior 
angle ; in others, near the middle. They live in the interior of madrepores, which they perforate. [“ This bivalve 
is inclosed in the posterior clavate extremity of a shelly tube, which is attenuated and open anteriorly, its aperture 
being oblong and bilobate, or nearly divided into two by a sort of septum which does not quite meet in the centre: 
this double aperture serves for the passage of the two tubes of the animal : the posterior extremity of the shelly 
tube is closed. This irregular clavate tube, already inclosing the two valves of the Gastrochaena, is generally found 
j within some other shell, to the inside of which it is attached, or it is protected in the ready-formed cavities of shells 
or rocks, or it lines cavities perforated by the animal itself in rocks, shells, or corals, and in this latter case, the 
1 double termination of the shelly tube projects beyond the surface of the coral or other object in which it is 
inclosed.”] 
Among fossils, two genera have been recognized furnished with tubes like the Teredo, but the first [Teredina, 
Lam.] has a little, spoon-shaped cavity in each valve, and a little loose piece, in form of a shield, at the hinge. 
The other {Clavagella, Lam.) has one of its valves agglutinated to the tube, and the other loose. A living species 
is found in the madrepores of the Sicilian seas, which has been described by M. Audouin. [The best description 
of this genus is given by Messrs. Broderip and Owen in the Trans, of the Zoological Soeiety^ 
Some naturalists think w^e should also place in this family 
The Aspergillum, — 
The shell of which is formed of an elon- 
gated, conical tube, closed at its widest ex- 
tremity by a disk perforated with numerous 
small tubular holes ; the little tubes of the 
outer range, being longest, form a kind of 
corolla round it. The reason for approxi- 
mating them to the Acephala with tubes is 
Fig 193 -Aspergillum. found in the fact that there is a double 
* According to Deslia5'cs, GastrociiBena and Fistulana are the same. — Eo. 
