ACEPHALA TESTACEA, 423 



single tooth in the middle of one valve, which penetrates between 

 two on the opposite one(l). 



PSAMMOTHEA, LaiTl. 



But a single tooth to each valve; otherwise resembling the Psam- 



mobi3e(2). 



Pholas, Lin. 



The Pholades have two broad valves, convex towards the mouth, 

 narrow and elongated on the opposite side, and leaving a large ob- 

 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, Petricolse, Sec. They are 

 much sought for on account of their agreeable flavour. 



Several species are found on the coast of France: such is the 

 Dail commiin; Pholas dactylus, L.; Chemn., VIII, ci, 859(3). 



Teredo, Lin. 



The mantle extended in a tube much longer than the two smally 

 rhomboidal valves, and terminated by two short tubes, the base of 

 which is furnished on each side with a stony and movable kind of 

 operculum or palette. These Acephala, while quite young, pene- 



(1) Tellina gari, L., Poll, 15, 23; — Solen vespertinus, Chemn., VI, 7, 59; — 

 Psammohia maculosa, Lam. ^ Egyp., Coq. pi. 8, f. 1; Psamm. elongata, Lara., 

 Egyp., pi. 8, f. 2. 



(2) Psammotheaviolacea, Lam., &c. 



N.B. These two s^enera are united in one by M. de Blainville, called Psammo- 

 coiA. On the whole, they differ but very slightly from the Sanguinolariae. Great 

 care is requisite in studying the shell, as the teeth are generally broken. 



(3) Add Pholas orientalis, lb., 860, which is, perhaps, a mere variety of dady- 

 lus; — Phol. costata, lb., 863; — Phoi crispata. Id., cii, 872, 874; — Phol. pusilla,lh ., 

 867, 871 ■■,— Phol. striata, lb., 864, 866. 



