PANAMIC-PACIFIC PELECYPODA 185 



1. Shell large, roundly cordate with high umbones and coiled beaks. 

 Interspaces narrower than the ribs. Posterior margin widely truncated. 



C. cuvieri 



2. Shell smaller, broadly subquadrate, the ribbed interspaces wider. Pos. 

 terior margin descending and narrowly rounded at the end. 



C. tricolor 



b. Shell thinner, the posterior-dorsal margin not furrowed. 



3. Shell small or of medium size, subovate, light-colored. 



C. spurca beehei 



B. Ribs wide and low between shallow, lined interspaces. No vestigial 

 tooth. 



4. Shell large, solid, trigonally rounded with high beaks, pointed, and 

 narrowly coiled. Color purple or brown under a coarse periostracum. 



C. megastropha 



II. Shell small to minute (length 3 to 5 mm.), lateral teeth present. 



5. Shell obliquely ovate with low ribs setoff by lined interspaces. 



C. guanica 



Cardita (Cardita) tricolor Sowerby Plate 26, figures 4-4c 



Cardita tricolor Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 194 Bay of Guayaquil. 



— Hertlein and Strong, 1946, Zoologica, vol. 31, pt. 3, No. 8, pp. 106, 107. 

 Cardita laticostata Sowerby, 1833, Proc. Zoo!. Soc. London for 1832, p. 195 Guacomayo. 



— Reeve, 1843, Conch. Icon., vol. 1, Cardita, pi. 7, figs. 36a, 36b, 36c. var. B., fig. 



36d (ref. to C. tricolor cited). — Maxwell Smith, 1944, Panamic Marine Shells, 



p. 56, fig. 709. 



Shell of medium size (length usually 45 mm., or smaller, rarely to 60 

 mm.), subquadrate, heavy and soHd, strongly ribbed. Umbones wide, the 

 small beaks placed near the anterior fourth. Sculpture formed by about 

 15, strong, squarish, coarsely noded ribs, their interspaces deeply grooved 

 and often cross-threaded, and nearly of the same width as the ribs them- 

 selves. Posterior-dorsal area excavated, more finely ribbed, vaulted in the 

 middle. Color pattern rather variable, usually with a white base mottled 

 by bands of brown of irregular shape and distribution, often only the top 

 of the ribs colored. Interior white or with a slight pink flush. The posterior- 

 dorsal margin descending, arched or slightly concave, its end narrowly 

 rounded. 



I have followed Lamy, and Hertlein and Strong in uniting C. tricolor 

 and C. laticostata as one species, although extreme shells may appear quite 

 different. Typical C. laticostata, so common at Panama, has a larger and 

 higher shell and the color pattern is a simple brown and white. The brown 

 spots frequently only paint the tops of the ribs, and do not penetrate into 

 the interspaces. Shells from Peru are usually smaller and longer with a 

 greater range of coloration, in which orange is frequently seen; these 

 shells were named tricolor by Sowerby and perhaps could be separated as 

 the typical subspecies but intermediate forms occur. 



Range — Gulf of California southward to Peru and the Galapagos 

 Islands. Panama: Burica Peninsula; Bucaro; San Carlos; Panama City. 

 Panama, Canal Zone: Venado Beach. Ecuador: Punta Blanca; Manta. Peru: 

 Tumbez; Zorritos; Punta Picos; Mancora. 



