94 AXEL A. OLSSON 



picked up on some open beaches, its usual habitat is lying deeply buried in 

 soft mud banks which border mangrove swamps; hence, its distribution 

 coincides closely with that of the mangrove. The southern limit^ of both 

 living Anadara grandis and of the mangrove is at the mouth of the Tumbez 

 River in northwestern Peru although fresh-looking shells of this ark washed 

 out of Pleistocene tablazo deposits occur as far south as Sechura Bay near 

 the northern border of the Peruvian faunal province, C. B. Adams, who 

 collected so extensively in Panama and carefully noted the ecological con- 

 ditions under which each species lived, recorded that this ark was found liv- 

 ing half buried in the mud and algae under trees a Httle above half tide level. 

 As fossil, Anadara grandis extends back into the Miocene at which time, 

 it spread into the Caribbean, generally occurring in beds with other brack- 

 ish-water species, often associated with lignites. 



Range — Lower California to Tumbez, Peru. Panama: San Miguel Bay; 

 mouth of the Rio Chepo. Canal Zone: Farfan Beach. Colombia: Buena- 

 ventura; Tumaco. Ecuador: Limones; Cojimenes; Manglaralto; mouth of 

 the Guayas River and adjacent shoreline southward to the Peruvian border. 

 Peru: Tumbez. 



Subgenus CUNEABCA Ball, 1898 



Type species by subsequent designation, Gardner, 1926, Area incongrua 

 Say. 



Shell trigonal, inflated, with full umbones and small, submedial and 

 slightly prosogyrate beaks over a high, triangular cardinal area covered 

 completely by the ligament. The cardinal area bared of the ligament is 

 smooth or marked obscurely with normal or longitudinal lines, the area 

 outlined by deep, side grooves to which the edges of the tensilium were 

 once attached. Hinge with numerous taxodont teeth in a continuous series, 

 small in the middle zone, larger at the ends. Valves slightly unequal, the 

 left valve being larger, its ventral margin overlapping, the external sculpture 

 discrepant, the ribs of the left valve larger, and more coarsely noded. Valve 

 margins strongly fluted. 



Anadara (Cunearca) bifrons (Carpenter) Plate 9, figures 3, 3a, 3b 



Area cardiiformis Sowerby, 1833, Proc. Zool. Soc. London, p. 22 San Bias, Gulf of 



California. — d'Orbigny, 1846, Voy. Amer. Merid., vol. 5, p. 634. Not A, 



cardiiformis Basterot, 1825. 

 Area bifrons Carpenter, 1856, Cat. Mazatlan Shells, Brit. Mus., p. 134, No. 184. 

 Scapharca (Cunearca) bifrons (Carpenter), Maury, 1922, Paleont. Amer., vol. 1, No. 



4, pp. 197-199, pi. 3, fig. 12. 

 Anadara (Cunearca) bifrons (Carpenter), Reinhart, 1943, Special Paper, Geol. Soc. 



America, No. 47, p. 70. 

 Area (Cunearca) bifrons (Carpenter), Hertlein and Strong, 1943, Zoologica, vol. 28, 



pt. 3, p. 160. 

 Area (Scapharca) corculum Morch, 1861, Malak. Blatter, bd. 7, p. 205. New name for 



Area cardiiformis Sowerby. 

 Area brasiliana Reeve, 1844, Conch. Icon., vol. 2, Area, pi. 3, fig. 17. Not of Lamarck. 



The shell figured is apparently A. cardiiformis from San Bias, Bay of California, 



and not the West Atlantic form. 



8 Anadara grandis was reported as living in Sechura Bay by Frizzell. This record 

 (s based either on fossil specimens washed out of tablazo beds such as found at Bayovar 

 or Recent specimens brought from the north by fishermen. 



