224 AXEL A. OLSSON 



B. Shell attached normally by its right valve, the beaks directed towards 

 the left. Sinistral Chamas. 



Genus Pseudochafna 



8. Color usually white or a light pink. 



P. tanamensh 



9. Color of interior and of the hinge teeth a deep purple, sometimes flushed 

 with white. 



P. corrugata 



10. Interior white, the outer surface white and pencilled with brown lines. 

 Galapagos. 



P. jamis (Plate 86, figure 5) 

 Genus CHAMA Linn6, 1758 



Type by subsequent designation, Schumacher, 1817, C. gryphoides 



Linne. Recent, Mediterranean sea. 



Dextral Chamas or in which the shell is attached by its left valve and 

 the beaks are directed or coiled towards the right side. Other characters 

 are those of the family. 



Cliama bnddiana C. B. Adams Plate 34, figures 2-2c 



Chama buddiana C. B. Adams, 1852, Ann. Lyceum Nat. Hist. New York, vol. 5, pp. 477, 

 544, No. 405 Panama — Maxwell Smith, 1944, Panamic Marine Shells, p. 56, 

 fig. 711. — ^Turner, 1956, Occas. Papers Mollusks, Mus. Comp. Zool., vol. 2, No. 

 20, p. 36, pi. 20, figs. 7, 8. 



Shell often large (height 120 mm.), suborbicular to subcircular, the 

 left valve attached to the substratum sometimes by more than half of its 

 surface so that only the rim of the posterior portion is free or the attachment 

 is by a smaller area along the anterior side of the umbone, the resulting 

 form is then more rounded and regular. The upper valve is smaller and 

 generally flatter than the lower, its height and length nearly equal but in 

 other more broadly attached specimens, the outline of the shell is subovate, 

 the height greater than the length. The external surface is often deeply 

 eroded or encrusted with marine growth, but good specimens, when cleaned, 

 may have an elaborate sculpture of rows of elevated, fluted white spines 

 standing on a red or purple base. On the lower valve, the spines are crowded, 

 coalescent, being the upturned edges of concentric lamellae while on the 

 upper valve, the spines stand separately. The outer layer of the shell is 

 relatively thin and forms a narrow, finely crenulated margin to the inner 

 surface of the valve. Interior of the valves white or blotched with lilac or 

 brown. 



This is the largest and commonest Chama at Panama (rarer elsewhere) 

 and is usually found attached to rocks at low or medium tide level. 



Range — Panama. Panama: Pearl Islands; Panama City; El Lagartillo, 

 near Las Tablas. Panama Canal Zone: Venado Beach. 



Chama echinata Broderip Plate 33, figure 3; 



Plate 86, figures 3, 3a 



Chama echinata Broderip, 1835, Proc. Zool. Soc. London for 1834, p. 150. — Broderip, 

 1835, Trans. Zool. Soc. London, vol. 1, p. 305, pi. 39, figs. 5-7.— Reeve, 1847, 

 Conch. Icon., vol. 4, Chama, sp. 35, pi. 7, fig. 35 Puerto Portrero. — Maxwell 

 Smith, 1944, Panamic Marine Shells, p. 56, fig. 715. — Hertlein and Strong, 

 1946, Zoologica, vol. 31, pt. 3, No. 8, pp. 108, 109. 



