ACEPHALA TESTACEA. 
109 
•narrow and elongated on the opposite side, and leaving a large oh- 
lique opening at each extremity ; their hinge, like that of a true Mya, 
is furnished with a plate projecting from one valve into the other, 
and with an internal ligament running from that plate into a cor- 
responding cavity. Their mantle is reflected externally upon the 
hinge, where it sometimes contains two or three supernumerary 
calcareous bodies. The foot issues through the aperture on the side 
next to the mouth, where it is widest, and from the opposite one 
project the two tubes, which are united and susceptible of inflation 
in every direction. 
The Pholades inhabit canals which they excavate, some in ooze 
and others in stone, like the Lithodomi, Petricolae, &c. They are 
much sought for on account of their agreeable flavour. 
Several species are found on the coast of France ; such is the 
Dail comviun ; Phola'i dactylus, L. ; Chemn., VIII, ci, 859 *. 
Teredo, Lin. 
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 stony and moveable kind of 
operculum or palette. These Acephala, while quite young, pene- 
trate and establish their habitations in submerged pieces of wood, 
such as piles, ships’ 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 Pholas excavates the wood 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 with a calcareous 
crust Avhich exudes from its body, and which forms a second kind of 
tubular shell for it. It is a noxious and destructive animal in the 
sea ports of Europe. 
Teredo navalis L. This species, which is the most common, 
and is said to have been introduced into Europe from the torrid 
zone, has more than once threatened Holland with ruin by the 
destruction of its dikes. It is upwaads of six inches in length, 
and has simple palettes. 
Larger species inhabit hot countries, whose palettes are articu- 
lated and ciliate. They should be remarked for their analogy to the 
Cirrhopoda. Such is the Teredo palmidatus , Lam., Adans., Ac. des 
Sc., 1759 , pi. 9, f. 12. 
Fistula N. t, Drug. 
Separated from Teredo; the extenial tube is entirely closed at its 
larger end, and is more or less like a bottle or club. The Fistulanse 
are sometimes found buried in submerged fragments of wood, or in 
* Add, Pholas orient alis, Ib., 860, which is, perhaps, a mere variety of dacfyh(s ; — 
Phol. cnsfafa, Ib., 863 ; — Phol. crispafa, Id., eii.,^872, 87-1 ; — Phol. pusillu, lb., 867, 
871 ; — Phol. striata, Ib., 864, 866. 
