PLATE LXII. 
I, 2. Plicatula Spinosa. ( Spinous Plicatula.) Obliquely-ovate, compressed, with an angle at 
the beaks; deeper valve, with radiating undulations and many, sharp spines; other valve concave, 
with irregular, hollow spines, frequently hooked ; margins entire. 
3, 4. P. Pectinoides. {Pectinated Plicatula.) Oblong-ovate, curved, depressed ; beaks curved, 
projecting; surface, with many, divergent ridges, with many, depressed spines; free valve concave. 
5. P. Inflata. {Inflated Plicatula.) Sub-orbicular, gibbose ; both valves convex ; beaks central, 
obtuse; surface smoothish, with a few, longitudinal ridges, each with a few, depressed spines. 
6. Pecten Cornells. ( Horny Pecten .) Orbicular, compressed, smooth, shining ; beaks promi¬ 
nent, well-marked ; ears small, equal ; with two, obtuse teeth in each valve ; shell thin, fragile. 
7. P. Cinctus. {Girdled Pecten.) Circular, gibbose; valves convex; ears small, with close 
ridges; with longitudinal strife ; edges entire ; shell thick. 
8. P. ObSCliruS. {Obscure Pecten.) Almost orbicular; compressed; ears largish; surface 
smooth, with obsolete, divergent sulci ; edge thick. 
9. P. Lamellosus. {Plated Pecten.) Orbicular; valves convex ; ears large, distant ; beaks 
rectangular; surface, with concentric laminae and divergent, small strife near the beaks. 
10. P. Rigidus. {Rigid Pecten.) Orbicular, compressed; hinge-line triangular; ears unequal, 
large ; surface, with strong, longitudinal striae and slender, concentric strife. 
II. P. Lens. {Lens-shaped Pecten.) Orbicular, convex, lenticular; surface, with divergent, 
arcuated, punctured striae ; shell thin. 
12. P. Beaveri. {Beaver's Pecten.) Orbicular, compressed; surface smooth, with irregular, 
longitudinal ribs ; ears equal; shell thin. 
13. P. Princeps. {Emperor Pecten.) Ovate, compressed; ears large, unequal, squamose; surface, 
with many, narrow ribs ; thickly covered with erect, concave scales; margins crenated. 
14. P. LaminatllS. {Laminated Pecten.) Sub-orbicular, compressed; ears unequal, triangular, 
the larger plaited; surface, with arcuated strife. 
15. P. ArCliatUS. {Arcuated Pecten.) Orbicular, compressed; ears large, dissimilar, larger one 
quadrangular, punctated ; side of shell arcuated ; surface, with punctated strife, and sometimes forked 
sulci. 
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