TRIBE FliCTtNIDED, 265 



margined with white. — Var. Tinged with violet botli externally 

 and at the inner margin. 4. Australia. This species u usually 

 longer (from the beaks to the ventral edge) than inM. Margaritifera ; 

 the nacre of its ear likewise projects more 



Section II. 



Ligament not marginal, inclosed in a short hollow under the beak, 

 always perceptible, and not forming a tendinous chord beneath the 

 shell. 



TRIBE PECTINIDES. 



Shell for the most part regular and not foliaceous : the ligament 

 either internal or partly so. 



PEDUM. 



Liequivalve, somewhat eared ; the lower valve gaping ; beaks un- 

 equal, separate ; hinge without teeth ; ligament partly external, 

 seated in an elongated hollow in the internal surface of the beaks ; 

 lower valve with a notch near the posterior dorsal margin. 

 P. Spondyloideum. Lam. 1. — Sow. G. — Reeve, t. 111. — Bl. 

 t. 62. f 6.— Ostrea. S. Gmel.3335.—D.p. 280.— Ch. f 669, 

 O.—E. t. 178. /. 1 to 4.— JF. t. 11. /. 15. Ovate wedge-shaped, 

 flat, whitish, slightly tinged with violet towards the beaks ; epider- 

 mis ferruginous : upper valve the larger, roughened by longi- 

 tudinal undulated granular striae. Var. 1 Smaller and rounded, 

 the lower valve the flatter. 3. Mauritius fy Indian Ocean. 



LIMA. 



Longitudinal sub-equivalve, with small ears ; valves slightly gaping 

 on one side ; beaks separate, their inner surface sloping outwards ; 

 cavity for the ligament partly external ; hinge without teeth. 



L. Scabra. Sow. Th. p. 83. t. 21. /. 4,5, 12.— Ostrea. S. 

 Born Mus. Cces. p. UQ.— W. t. 11. /. 55.— D. p. 271.— O. Glaci- 



alis. Gmel. — Pecten Aspera. Ch. f. 653. — Lima G. Lam. 3. 



Sow. G.f. 1.— Reeve Sys. t. 112. /. \.—E. t. 206. /. 2. Oval, 

 thick, rather compressed, slightly gaping at the anterior margin, 

 rather more so at the posterior ; surface rendered scabrous by an- 

 gularly notched ribs meeting in the centre at an angle : ears striated 

 the posterior tumid and slightly reflected : epidermis brown ; hinge 

 thick and obsoletely plaited. Sometimes this species becomes irreou- 

 larly tongue shaped. 1,40.. 2. W. Indies. 



