166 ARCID^E. 



not seem expedient to substitute it for the long-esta- 

 blished name given by Lamarck. 



1. Pectunculus glycy'meris *, Linne. 



Area glycymeris, Linn. Syst. Nat. p. 1 143. P. glycimeris, F. & H. ii. p. 245, 

 pi. xlvi. f. 4-7, and (animal) pi. P. f. 6. 



Body nearly round and compressed, yellowish-brown : 

 mantle thick, covered with minute specks of brown and flake- 

 white ; it is quite open on the anterior side, and but slightly 

 contracted on the other side : the edges on the posterior side 

 are studded with numerous, small, black, eye-like tubercles : 

 foot very large, axe-shaped, deeply cloven or folded length- 

 wise when not in action. 



Shell slightly compressed, very thick and solid, of a dull 

 hue : sculpture, numerous fine longitudinal striaj, and more 

 remote impressed lines, which are crossed by transverse or 

 concentric striae, varying in number and strength, the surface 

 being thus often reticulated : colour yellowish-white, irre- 

 gularly mottled with zigzag streaks or blotches of purplish 

 brown, or marked with spots or longitudinal lines of the same 

 colour, sometimes of a beautiful pink or lighter tint, and even 

 milk-white : epidermis brown and thick, forming rows of 

 short bristles on the impressed lines in young specimens : mar- 

 gins rounded on all sides except at the back, where they are 

 interrupted by the beak and hinge -line : beaks small and pro- 

 minent, incurved : ligament dark brown, consisting of eight or 

 nine bundles, which are placed in a large triangular and grooved 

 cavity below the beak ; these bundles are consequently longer 

 at each end, the shortest being in the middle : hinge-line semi- 

 circular : hinge-plate also curved, extremely broad and thick, 

 occupying two-sevenths of the circumference : teeth set ob- 

 liquely, six or seven in the adult (besides a few others of a 

 smaller size) on the anterior side, and nearly as many on the 

 posterior side, the intermediate space being smooth ; in younger 

 shells the number of primary teeth is the same, but the middle 

 area is furnished with four or five minute teeth : inside yel- 

 lowish, with a purple tinge in some parts, freckled or closely 

 pit-marked, bevelled towards the margin, Avhich is broad and 

 strongly notched at the edge : muscular scars very conspi- 

 cuous. L. 2-25. B. 2-25. 



* A name given by Pliny to a kind of shell-fish. 



