92 AXEL A. OLSSON 



hinge line. Beaks small, placed at the anterior one-third and usually with a 

 small black stain, weakly sulcated across the umbones. Ribs 28 to about 30, 

 flat between squarish interspaces, wider posteriorly, the anterior ribs usually 

 finely noded. Cardinal area long and narrow, completely covered by the 

 ligament. 



Length 38.6 mm., height 17.5 mm., diameter 15.2 mm. 



Zorritos, Peru. 



Range — Lower California to northern Peru. Panama: Panama City, 

 Bucaro. Ecuador: Mompiche; Sua; Santa Elena. Peru: Tumbez; Zorritos; 

 Lobitos; Paita. 



Subgenus LABKINIA Reinhart, 1935 

 Type species by original designation, Anadara larkinii (Nelson). 



Shell subtrigonal, nearly as high as long, solid and heav-y, with high, 

 prominent umbones and small prosogyrate beaks. Posterior side subtruncate, 

 flattened to deeply impressed, generally with the umbonal angle prominent. 

 Cardinal area high, subtrigonal, covered by the ligament, and marked off 

 by a deep groove on each side, its surface smooth or covered with trans- 

 verse, ligamental grooves. Ribs numerous, narrow, between square- or steep- 

 walled interspaces, the summit of the ribs beaded with coarse or scabrous 

 nodes. Hinge teeth numerous, continuous, vertical in the middle, oblique, 

 and divergent at the ends. 



Atiadara larkinii is a fossil species from the upper Miocene and Pliocene 

 of Peru and Ecuador. It has a coarse, solid shell with high central umbones 

 and small beaks placed above a high cardinal area, which is at first smooth, 

 later becoming marked with crowded, transverse grooves. The subgenus is 

 well represented by numerous fossil species in the Caribbean Miocene 

 (A. chiriquiensis Gabb). 



Anadara (Larkinla) multlcostata (Sowerby) Plate 7, figure 5; Plate 9, figure 6 



Area multlcostata Sowerby, 1833, Proc. Zool. Soc. London, p. 21 Gulf of Tehuantepec. — 



Reeve, 1844, Conch. Icon., vol. 2, Area, pi. 4, fig. 23. 

 Seapharea (Seapharea) multieostata (Sowerby), Maury, 1922. Paleont. Amer., vol. 1, 



No. 4, p. 195. 

 Area (Larkinia) multieostata Sowerby, Hertlein and Strong, 1943, Zoologica, vol. 28, 



pt. 3, p. 162. 

 Anadara (Larkinia) multieostata (Sowerby), Reinhart, 1943, Special Paper, Geol. Soc. 



America, No. 47, p. 66, pi. 8, figs. 9-11.— Durham, 1950, Mem. Geol. Soc. 



America, No. 43, p. 54, pi. 1, figs. 15, 16, 17.— Rost, 1955, Allan Hancock 



Pacific Expeditions, vol. 20, No. 2, p. 196, text-figs. 84 a-d. 



Shell large, subquadrate or squarish, solid, with wide, prominent and 

 nearly median umbones terminating in small, prosogyrate beaks above a 

 medium-height cardinal area. Posterior umbonal slope subangular, the pos- 

 terior margin straight as if truncated. Anterior side short, rounded at the 

 margin and somewhat shortened at the hinge as if slightly auriculate. 

 Cardinal area fully covered by the ligament and carved with one or more 

 chevron-shaped grooves. Valves are nearly alike, convex, the beaks not 

 sulcated, the ventral marginal overlap almost lacking. Ribs numerous (about 

 33), narrowly rounded, and of about the same width as their interspaces, 

 smooth except along the anterior umbonal slope where they are finely 

 and sharply noded. Periostracum brown, rather copious and neatly con- 



