98 AXEL A. OLSSON 



Anadaia (Sectlarca) conclnna (Sowerby) Plate 8, figures 1, la 



Area concinna Sowerby, 1833, Proc. Zool. Soc. London, p. 20. — Reeve, 1844, Conch. Icon., 



vol. 2, Area, pi. 6, fig. 34. 

 Area (Seapharea) concinna Sowerby, Hertlein and Strong, 1943, Zoologica, vol, 28, 



pt. 3, pp. 162, 163.— Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. Hist, 



vol. 107, art. 2, p. 172, pi. 2, fig. 20. 

 Seapharea (Seapharea) concinna (Sowerby), Maury, 1922, Paleont. Amer., vol. 1, No. 



4, p. 25, pi. 1, fig. 10. 

 Area cumingiana Nyst, 1948, Mem. Acad. Roy. Sc. Lett Beaux-Arts, vol. 22, p. 22. 



(New name'for concinna Sowerby, non concinna Phillips 1829, as Cueullaea). 



Shell of medium size, elongately ovate, somewhat cylindrical and 

 evenly convex, the ratio of height to length about 1 to 2, the dorsal and 

 ventral margins straight and nearly parallel, the two ends olsliquely rounded. 

 Sculpture consists of about 28 to 31 ribs, the anterior divided by a medial 

 groove and strongly noded, their interspaces laced by finer cross concentrics; 

 the other ribs are simple and smooth. The anterior section of the cardinal 

 area is smooth, the posterior section traversed by 1 to 3 oblique grooves. 



Length 33.5 mm., height 19 mm., diameter 15.6 mm. 



Fort Amador Beach, Balboa, Canal Zone. 



This species appears to be locally common in waters of 10 fathoms or 

 more but is rarely found on the beach. It is especially common in the 

 mud dredged from the entrance of the Panama Canal at Balboa and Palo 

 Seco. This species is similar to several fossil forms from the Miocene such 

 as A. inaequilateralis Guppy from Jamaica and Santo Domingo and A. 

 daiiensis Brown and Pilsbry from Panama. It occurs as a Pliocene fossil 

 in Ecuador. 



Range — Gulf of California to Ecuador. Costa Rica: Gulf of Nicoya. 

 Panama: Bucaro; Burica Peninsula; Canal Zone: Palo Seco; Fort Amador. 

 Ecuador: Off Esmeraldas; Off Cabo Pasados; Charapota; Punta Blanca. 



Subgenus CALOOSARCA, new subgenus 



Type species, Anadara rustica (Tuomey and Holmes). Pliocene of 

 South Carolina and Florida. 



Shell broadly elongate, moderately heavy, equivalve, convex. Cardinal 

 area elongate, rather low or narrow, not covered fully by the ligament, the 

 small portion anterior to the beaks usually bare. Posterior side deeply im- 

 pressed, often winged or emarginated. Ribs simple, plain or heavily noded 

 and often differing considerably in size, the anterior set sometimes mesially 

 grooved. Hinge teeth small, numerous and in a continuous series. 



In the average specimen of A. rustica, the cardinal area in front of 

 the beak is bare, but in gerontic specimens the anterior area may be partly 

 covered or furrowed with ligamental grooves. In A. notabilis of the 

 Caribbean, the cardinal area has essentially the same characters as in .4. 

 rustica (see Plate 8, fig. 3). 



Anadara (Caloosarca) blangrulata (Sowerby) Plate 8. figures 5. 5a, 5b 



Area biangulata Sowerby, 1833, Proc. Zool. Soc. London, p. 21. (Atacames). 



