PANAMIC-PACIFIC PELECYPODA 293 



Antigona {Ventricola) isocardia magdalenae (Dall), Hertlein and Strong, 1948, Zoologica, 

 vol. 33, pt. 4, p. 179. 



According to Dall, 1902, this is the Pacific analogue of A. strigUlina of 

 the Atlantic fauna, but thinner, less inflated, with more delicate sculpture, 

 and pale yellowish coloration spattered with brown flecks. According to 

 Hertlein and Strong, young shells differ from those of A. isocardia in having 

 a more elongated form and a finer sculpture but in other respects, they 

 considered the resemblance to A. isocardia so great as to justify only a sub- 

 specific separation. 



Range — Along the west coast of Lower California and into the Gulf 

 of California. Dall also recorded this species from Panama Bay in 18 

 fathoms, but this occurrence has not been checked. 



Genus PERIGLTPTA Jukes-Browne, 1914 

 Type species by original designation, Venus puerpera Linne. 



Shell medium size to large, subovate, rotund, convex, and with a can- 

 cellate sculpture of large, narrow, rounded, concentric ridges, their sides 

 and tops frilled or crenulated by simple radial riblets, also present in the 

 interspaces. An escutcheon is present in both valves, that of the left valve 

 is medially grooved. Lunule small, cordate, concentrically sculptured, cir- 

 cumscribed by an incised line. Ligament deeply inset, partly overlapped 

 by the edge of the escutcheon of the right valve. Hinge plate solid, with an 

 excavated margin, the middle and posterior cardinal teeth of the right 

 valve and the middle cardinal tooth in the left valve are bifid. A small, 

 often pimple-like lateral tooth at the base of the anterior cardinal tooth is 

 present in the left valve; a lateral pit is sometimes indicated in the right 

 valve. The impression of the pedal muscle scar under the hinge plate below 

 the anterior cardinal tooth is large and deep. Ventral margins smooth or 

 irregularly crenulate. 



Perlglypta multlcostata (Sowerby) Plate 50, figures 3-3b 



Fenus multicostata Sowerby, 1835, Proc. Zool. Soc, p. 22. — Sowerby, 1853, Thes. Conch., 



vol, 2, p. 706, pi. 152, fig. 10. — Reeve, 1863, Conch. Icon., vol, 14, Venus, pi, 9, 



fig. 3. 

 Antigona multicostata (Sowerby), Maxwell Smith, 1944, Panamic Marine Shells, p. 



60, fig. 765. 

 Antigona (Dosina) multicostata (Sowerby), Van Winkle Palmer, 1927, Paleont. Amer., 



vol. 1, No. 5, pi. 30, fig. 11. 

 Antigona (Periglypta) multicostata (Sowerby), Hertlein and Strong, 1948, Zoologica, 



vol. 33, pt. 4, p. 178. 



This is a large, heavy-textured shell, often reaching a length of 115 

 mm., the surface sculptured with large, coarse, flat-topped or reflexed, con- 

 centric ridges coarsely crenulated by radials. Well-cleaned specimens are 

 mostly white or cream-colored but with the umbones finely variegated 

 with brown lines. This fine clam is locally plentiful in the Pearl Islands, 

 Panama, where it is gathered as a highly esteemed sea food. A closely related 

 form [P. caribbeana Anderson (P. dominicana Van Winkle Palmer)] occurs 

 in the Miocene of the Dominican Republic, northern Colombia, and in 

 Panama and is mainly distinguished from the Recent species by its more 

 rounded form and less strongly crenulated concentrics. 



Range — Lower California to Peru and the Galapagos Islands. Panama: 

 Pearl Islands, Ecuador: Manta; Isla la Plata; Santa Elena. Peru: Cabo 

 Verde. 



