134 INVERTEBRATA OF MASSACHUSETTS. 



Shell sub-orbicular, or broadly ob-ovate, equal, the upper 

 valve slightly more convex than the lower, covered with an in- 

 definite number, fifty to a hundred, of narrow, unequal, crowded, 

 irregularly disposed, radiating ridges, bearing a multitude of erect, 

 vaulted scales ; their ridges are grouped, so as to form a number 

 of unequal ribs, which are better defined on the interior of the 

 shell. Ears unequal ; posterior one shortest, and its angle slightly 

 obtuse, alike in both valves, and covered with scaly, radiating 

 ridges ; the anterior ear of the right valve is more deeply notched 

 than that of the left, and has five radiating ribs, occupying about two 

 thirds of its surface. Valves closed except at the notch ; color 

 passing from light-orange to dark reddish-brown ; the upper valves 

 usually zoned, or blotched, with deeper colors, and the lower 

 valve much the lightest. The margin jagged by the elevated 

 lines, all but the notch of the right valve, which is plain, except- 

 ing that there are five or six minute teeth in the angle. Interior 

 white and glossy, the left valve usually having a large roseate spot 

 near the beaks. Length 3 inches, height 3| inches, breadth 1 

 inch. 



Occasionally found, of a small size, in the stomachs of fishes. 

 Its proper residence, however, seems to be the Newfoundland 

 Banks, where it is a favorite food of fishes. 



In a young state the vaulted scales do not appear ; but the inter- 

 stices between the ribs are filled with a beautiful lozenge-shaped or 

 tile-work sculpture, which may usually be seen near the beaks in 

 adult specimens. The coloring varies greatly, and has given rise to 

 two or three synonyms. 



Pecten conce'ntricus. 



Shell orbicular, ears sub-equal, valves convex, nearly closed, 

 with about twenty rounded ribs. 



Figure 88. 

 State Coll., No. 150. Soc. Cab., No. 2036. 



Pecten concentricus, Say; Journ. Acad. JVat. Sc, ii. 259. Conrad; Amer. 

 Mar. Conch., pi. 1, f". 2. 



Shell nearly round, rather strong ; valves convex, the lower 

 very little less so than the upper one, with about twenty elevated. 



