178 PHOLADIDA. 
about twelve whitish-brown rays, of deeper timt towards the 
base, and between some of them one or two smaller, but not 
fimbriated; the anal has about eight short pale rays. Some 
authors describe papille on the tubes; our specimens only 
showed minute sand-like pomts, which we think are due to 
the epidermis. The foot is much narrower, more elongated 
and pointed than in any of its congeners, and fixed to the 
body by a compressed pedicle, of a pale hyaline in some 
animals, and flaky bluish-white in others. All the other organs 
exhibit no particular variation from those of P. dactylus. 
P. crispata, Linneus. 
P. crispata, Brit. Moll. i. p. 114, pl. 4. f. 3, 4, 5. 
This Pholas does not inhabit the South Devon coasts. 
The P. striata of authors is exotic. 
I have so fully entered on the boring qualities of the 
Pholades in the January Number of the ‘ Annals’ for 1850 
as to render further remarks unnecessary. The Pholades are 
generally excavators and inhabitants of rocks, chiefly the red 
sandstone on the South Devon coast, but the P. dactylus and 
P. candida often burrow and pass their existence im pure 
sand, at the back of the Warren and Cockle Sands at Exmouth, 
where the finest and most delicately sculptured individuals 
are found, surpassing in beauty the rock specimens. 
Having concluded my remarks on the external organs of 
the Pholades, I shall now proceed to the anatomy of the Pholas 
dactylus, connecting with it the parts of the shell that relate 
to the hinge, cartilage, ligament, curved subumbonal apo- 
physes, and other accessories: for reference, and to prevent 
confusion, I have distributed the matters to be considered 
into distinct sections. 
The Hinge. 
The hinge of the Pholades appears not to be well under- 
stood, and has not received the investigation that has been so 
liberally bestowed on the terebrating powers of the animal ; 
