MALAC020A. TROPIOPODA. LAMELLIBRANCHIATA. 223 



twecn which are oculiform tubercles. The mouth rather 

 large, oval, with prominent, deeply cut lips, and on 

 each side a pair of truncated palpi. Branchiae large, 

 divided into filaments. Adductor muscle very large, 

 subcylindrical, subcentral. 



Shell free, regular, inequivalve, roundish, compressed, 

 divergently costate ; umbones very small, pointed, di- 

 rect, contiguous. Cardinal space narrow, elongated into 

 a straight margin, with a triangular pit, and divergent 

 lateral grooves and ridges, in each valve ; lateral teeth 

 remote, in one valve an elongated obtuse rib on each 

 side, in the other a notched prominence. Ligament in- 

 ternal, trigonal, received by the cardinal pits. A single 

 very large muscular impression. 



1. Ptcten maxlmus. Great Scallop. 



Shell nearly orbicular, inequivalve; the lower valve con- 

 vex, with sixteen convex ribs, which, with their nearly equal 

 convex interstices, are longitudinally striate ; upper valve flat, 

 toward the hinge concave, with sixteen convexo-depressed ribs, 

 which, with their wider concave intervals are finely lamelloso- 

 striate ; the auricles nearly equal, and divergingly costato-ru- 

 gose ; externally the lower valve yellowish-white, the upper 

 chiefly brownish-red ; internal surface glossy, smooth, with a 

 large roundish, muscular impression, and toward the margin 

 marked with prominent flattened, marginate ribs, white, the 

 upper valve margined with red ; margins of convex valve ex- 

 tending beyond those of the other. Greatest length of the 

 largest specimen obtained by me six inches, height five inches 

 and eight-twelfths. Its greatest diameter however is some- 

 times nine inches. 



In deep water, on hard ground, off the coast. Dead valves 

 very frequently brought up by the lines. In the Winter of 

 1841, I obtained a recent shell, three inches long; and in the 

 Summer of 1842, a valve of another found on the beach by 

 the preventive-service people, six inches in diameter. Miss 

 Macgillivray procured one measuring four inches and ten- 

 twelfths, by five inches and a quarter, at Gamrie, in Septem- 

 ber. 



Peclen maximus, circiter 14 striis. Lister. Anim. Angl. 184. 

 PI. 5. f. 29. Ostrea maxima. Linn. Syst Nat. i. 1144. Pecten 

 maxiinus. Turt. Brit. Biv. 207. Pi-cU'ii maximus. Flem. Brit. 



