216 AXEL A. OLSSON 



left valve. Ligament deeply immersed, overhung by the valve margin so 

 that it is scarcely visible from above and attached to a broad, deeply exca- 

 vated scar, its inner portion (resilifer), often abutting against the cardinal 

 teeth. Hinge with a small and a large, cardinal tooth in each valve, also 

 lateral teeth; the anterior lateral tooth or its socket is strong, the pos- 

 terior lateral tooth absent in the restricted genus. The adductor scars are 

 distinct, the anterior one is divided into two parts, the lower portion 

 elongate and narrow, free from the pallial line. Surface white, the interior 

 white or yellow, sometimes with a purplish red border. The genus may be 

 divided into two groups as follows: 



I. Shell large, depressed or slightly convex. Posterior lateral teeth obsolete. 

 Interior of shell white, yellow or some shade of red, often with a wide 

 marginal band of red or purple. 



Codakia s.s. 



II. Shell much smaller and generally convex. Posterior lateral teeth strong. 

 Interior of shell usually white, no marginal band. 



Subgenus Ctena 



Subgenus CODAKU, s.s. 



Shell often large and heavy, subcircular, white, the interior often 

 yellow with a coral-red or purple border. Hinge with a strong anterior 

 lateral tooth in the right valve, its socket in the left; the posterior lateral 

 tooth absent. 



Three species in the Panamic area. 



Key to species of Codakia 



I. Surface sculptured with large, flat ribs separated by grooved inter- 

 spaces, the spacing and size of the ribs irregular, sometimes obsolete 

 across the middle. 



C. punctata 



II. Surface sculpture much finer, the riblets small and numerous, finely 

 beaded by threadlike concentrics. 



A. Shell coarse and heavy, often large, depressed to slightly convex. 



C. distinquenda 



B. Shell smaller, more convex and somewhat more coarsely sculptured. 



C. finchoti 



Codakia (Codakia) punctata (Ldnn6) Plate 29, figure 1 



Veiius punctata Linne, 1758, Syst. Nat, 10th ed. p. 688, No. 116; 1767, 12th ed., p. 1134, No. 



140. Habitat in O. Indico. 

 Lucina punctata (Linne), Reeve, 1850, Conch. Icon., vol. 6, Lucina, pi. 1, fig. 2 "Panama" 



in sand at low water, Cuming. 



This species has been considered strictly an Indo-Pacific form. 

 However, an excellent figure of this species is given by Reeve from a speci- 

 men taken by Cuming at Panama. The Academy of Natural Sciences has 

 in its collection a double-valved shell also labeled Panama (Swift Coll. 

 ANSP 54393) which in all probability came from the original lot collected 

 by Cuming. Further substantiation of the occurrence of C. punctata in the 

 eastern Pacific is furnished by another specimen in the Academy of Natural 

 Sciences (ANSP 170324) from Wreck Bay, Chatham Island, Galapagos. 



