PANAMIC-PACIFIC PELECYPODA 205 



Lucina caelata Reeve, 1850, Conch. Icon., vol. 6, Lucina, pi. 6, figs. 27a, 27b Island of 



Muerte, Bay of Guayaquil. 

 Diplodonta {Phlyctiderma) caelata (Reeve), Dall, 1901, Proc. U.S. Nat. Museum, vol. 



23, No. 1237, p. 796. 

 Taras {Phlyctiderma) semirugosa (Dall), Hertlein and Strong, 1947, Zoologica, vol. 



31, pt. 4, p. 132. 

 Diplodonta {Phlyctiderma) semirugosa Dall, Hertlein and Strong, 1955, Bull. Anaer. 



Mus. Nat. Hist., vol. 107, art. 2, p. 185, pi. 2, figs. 12, 16, 17. 



Shell of medium or large size (average length about 21 mm.), sub- 

 circular, rounded and convex, thin or subsolid, white or light gray. Umbones 

 full, the small beak placed at the anterior one-third. Surface with coarse 

 concentric sculpture, generally breaking apart to form large nodes which 

 cover the general disk except along the posterior dorsal slope. 



Length 21.5 mm., height 19.7 mm., semidiameter 8.6 mm. Manta, 

 Ecuador. 



A comparison of specimens of P. caelata from Ecuador and Peru with 

 P. semiaspera from Florida reveals no essential difference between them. 



Range — Coast of Ecuador and northwestern Peru. Also West Atlantic. 

 Ecuador: Manta; Puerto Callo. Peru: Boca Pan; Mancora; Sechura. 



rhlyctJderma Insula, new species Plate 32, figure 9 



Shell relatively small (length about 8.5 mm.), white, rounded, globose, 

 the umbones large and prominent with the beaks prosogyrate and placed 

 almost median. Viewed internally, the two ends of the shell appear almost 

 of the same size and well rounded, the anterior slightly shorter. Shell thin, 

 glassy to subtranslucent, internally white with a subnacreous luster. Surface 

 marked with fine, smoothish, growth lines and a scattering of small nodes 

 or pustules, many of which are finely punctured or appear hollow. These 

 pustules are thickly or thinly developed on the anterior half of the disk, 

 lacking on the posterior side. 



Length 8.5 mm., height 7.5 mm., semidiameter 3 mm. a left valve. 

 Holotype, ANSP. 



Resembles P. caelata but is much smaller, with a somewhat different 

 form and the pustules are rounded, mostly concentric in their alignment. 



Range — Panama and western Colombia. Panama: Bucaro. Colombia: 

 Isla del Gallo. 



Phlyctiderma elenensis, new species Plate 32, figures 6, 6a 



Shell small (length about 9 mm.), rounded and plump, the umbones 

 submedian, wide and full, projecting prominently above the hinge line. 

 Beaks are small and prosogyrate. Anterior side longer, somewhat produced 

 and narrowly rounded at the end while the posterior and ventral margins 

 unite to form part of the same circular curve. The hinge line is straight 

 and projects a little beyond each side of the beaks. In the type, the hinge 

 teeth are poorly developed (perhaps the result of damage), the posterior 

 cardinal tooth is simple and a little inclined; the anterior tooth appears 

 to be missing. Ligamental scar is partially immersed, set apart by a groove 

 to which the external ligament is attached, the margin of the valve not 

 rising above it. Adductor scars large and subequal, connected by an entire 

 pallial line which lies close to the ventral margin. Sculpture produced by 



