PANAMIC-PACIFIC PELECYPODA 83 



cavity or crevice in which the shell once nestled. The valves are often 

 heavily encrusted with marine growth. Color white. When in good condi- 

 tion, the surface sculpture is quite elaborate and formed by strong, con- 

 centric ridges and smaller cordlike radials, their intersection forming sharp, 

 rasplike nodes. Along the posterior umbonal slope, the concentrics are 

 elevated, forming a sharply crenulated or fluted lamina. 



The holotype of the species has been illustrated by Reinhart. 



The species is closely related to A. reticulata (Gmelin) from the Carib- 

 bean. Common under stones or nestling in abandoned worm burrows, 

 crevices, and the like. 



Range — Lower California to northern Peru and the Galapagos. 

 Panama: Panama City. Canal Zone: Venado Beach. Ecuador: Santa Elena; 

 Isla la Plata; Manta; Cabo Pasados; Mompiche; Galeras; Esmeraldas. Peru: 

 Tumbez; Zorritos; Boca Pan; Caleto Sal; Mancora; Lobitos; Negritos; 

 Paita. 



Genus FULGERIA Reinhart, 1937 



Type species by original designation, Barbatia (Fulgeria) pseudoillota 

 Reinhart, 1937. Pliocene of ^4eri^a. '- ^- ^ > ^o< ^^ > r^ f . < > ,: V. „ , c y ^1 



Shell subequivalve, convex, thin, white under a black or brown sub- 

 pilose or foliated periostracum. Cardinal area like that of Acar with the 

 ligament narrow and developed principally on the posterior side, the 

 anterior section bare. Hinge that of Barbatia, the posterior set of teeth 

 well developed or subobsolete. The sculpture is formed by small, threadlike 

 riblets, weakly cancellated by concentrics. 



The Recent species of this subgenus have a thin, white shell under a 

 black or brown, subpilose or foliated periostracum, generally thinly de- 

 veloped over the umbones, more profusely so around the ventral margin 

 where it may form into thin, loose, leaflike ribbons, finely serrated at 

 the ends. 



Fulgeria illota (Sowerby) Plate 6, figures 1, la, lb 



Byssoarca illota Sowerby, 1933, Proc. Zool. Soc. London, p. 18 Gulf of Nicoya. 

 Area illota (Sowerby), Reeve, 1844, Conch. Icon., vol. 2, Area, pi. 12, fig. 78. 

 Area (Byssoarea) Tabogensis C. B. Adams, 1852, Ann. Lyceum Nat. Hist. New York, vol, 



5, pp. 486, 545, No. 424. — Turner, 1956, Occas. Papers on Mollusks, Mus. Comp. 



Zool., vol. 2, No. 2D, p. 90, pi. 19, figs. 7, 8. 

 Barbatia (Acar) illota (Sowerby), Maury, 1922, Paleont. Amer., vol. 1, No. 4, pp. 182, 



183, pi. 2, figs. 8, 14. 

 Barbatia (Fulgeria) illota (Sowerby), Reinhart, 1943, Special Paper, Geol. Soc, America, 



No. 47, p. 37. — Rost, 1955, Allan Hancock Pacific Expeditions, vol. 20, No. 2, 



pp. 187, 188, pi. 11, figs. 6-8; text-figs a-c. 



The shell is small or of medium size (length 37 mm,), subquadrate to 

 trapezoidal, generally thin, convex, with a shallow sulcus across the middle 

 to the ventral margin. Color of shell beneath the brownish periostracum 

 is white. Ribs are small, threadlike, finely cancellated by the concentrics. 

 The periostracum is quite copious, covering the whole disk, except the 

 umbones which are sometimes bare, and consists of broad, thin, leaflike fila- 

 ments, finely serrated at the end, and most heavily developed along the 

 ventral margin. 



Length 32.3 mm., height 22 mm., diameter 14 mm. 



Palo Seco, Canal Zone. 



