102 AXEL A. OLSSON 



sionally flexed, its end produced and pointed. Anterior side longer, rounded 

 to subquadrate in shape. Ribs, which number usually about 25, are flat 

 and rather broad, close-set and wider anteriorly, narrower and more widely 

 spaced posteriorly. The ligament lies wholly anterior of the beaks. Perio- 

 stracum coarse and heavy, concentrically scaly, pilose, and of a velvety, 

 dark-brown color. 



Several names have been given to fossil forms of Noetia from the late 

 Tertiary beds of the Pacific and Caribbean coastal lands of Central America 

 and northern South America, many of which are so similar to N. reversa 

 that they could well be considered as subspecies of the Recent shell. Some 

 fossil Noetias attain a much larger size (up to 85 mm.), than the Recent 

 shell. Most specimens of N. reversa are quite regular in shape but some 

 shells from Sua, Ecuador, are strongly produced posteriorly and resemble 

 the Miocene N. macdonaldi Dall from the northeast coast of Costa Rica. 



Range — Lower California to northwestern Peru. Panama: San Carlos; 

 Bucaro; Chepo. Colombia: Isla del Gallo; Choco. Ecuador: Galeras; Sua; 

 Manta; Isla la Plata; Santa Elena. Peru: Tumbez; Zorritos; Boca Pan; 

 Mancora. 



Subgenus EONTIA MacNeil, 1938 



Type species by original designation, Area ponderosa Say. Recent, 

 East Coast of the United States, Massachusetts to northern South America. 



Ligament not wholly restricted to the anterior side, a small segment 

 not vertically grooved, present on the posterior side. Ribs less flattened 

 and divided by wider interspaces. 



An East American group but with one species on the Pacific Coast. 



Noetia (Eontia) olssoiii Sheldon and Maury Plate 10, figures 2, 2a 



Noetia olssoni Sheldon and Maury, 1922, Paleont. Amer., vol. 1, No. 4, pp. 10, 11, pi. 



1, fig. 9. 

 Eontia olssoni (Sheldon and Maury), MacNeil, 1939, Prof. Paper 189-A, U. S. Geol. 



Survey, p. 13, pi. 1, fig. 19, 20. 

 Noetia {Eontia) olssoni Sheldon and Maury, Reinhart, 1943, Special Paper, Geol. Soc. 



America, No. 47, p. 77, pi. 2, figs. 13, 14. 



Shell small, (the largest seen, about 27 mm.), elongate-subtrigonal, the 

 umbones high, convex, nearly central, ending in a small, narrow, curved, 

 pointed beak seated above the cardinal area. The umbonal angle is strong 

 and sharp, extending to a pointed posterior end. Anterior side is long, 

 narrowed, rounded at end. Sculpture consists of numerous, small, narrow 

 beaded riblets separated by interspaces carrying an interstitial thread. 

 Cardinal area an unequal-sided triangle, the short side posteriorly, the 

 longer anterior portion vertically grooved. Ligament completely covers 

 the cardinal area, the larger part on the anterior side. Surface covered by 

 a thin periostracum, generally worn off in beach shells. Ventral margin 

 sinuous, toothed on the anterior and posterior sides. Beaks usually colored 

 pink. 



This species is closely related to N. centrota (Guppy) from the south- 

 ern Caribbean but has smaller, narrower umbones and a more compressed 

 posterior side. Both the Caribbean and Pacific species have the umbones 

 colored pink. 



Range — Panama southward to Peru. Panama: Burica Peninsula; 



