178 PHOLADID^E. 



about twelve whitish-brown rays, of deeper tint 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 papillae on the tubes; our specimens only 

 showed minute sand-like points, 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. dactylics. 



P. CRISPATA, Linnaeus. 

 P. crispata, Brit. Moll. i. p. 114, pi. 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 in 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 ; 



