PANAMIC-PACIFIC PELECYPODA 3(S 



Semele fonnosa (Sowerby) Plate 85, figure 8 



Amphidcsma formosum Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 199 "Santa 



Elena". — Sowerby, 1833, Conch. Illust. fig. 8. 

 Amphidesma formosa Sowerby, Reeve, 1853, Conch. Icon., vol. 8, Amphidesma, pi. 4, 



fig. 27. 

 Semele formosa (Sowerby), Maxwell Smith, 1944, Panamic Marine Shells, p. 62, fig. 801. 



Shell broadly subovate, thick, the posterior side a little shorter than 

 the anterior, strongly flexed. Surface marked with rather coarse, regular 

 concentrics. Basal color white interrupted by narrow purple bands follow- 

 ing the resting marks and faintly variegated over the umbones and broadly 

 rayed on the middle and ventral surface of the disk. 



Length 64.4 mm., height 52 mm., diameter 27 mm. 



Range — Gulf of California ? south to Ecuador, Ecuador: Santa Elena 

 (Brit. Museum Nat. History.) 



Semele pnnctata (Sowerby) Plate 64, figure 2 



Amphidesma punctatum Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 200 Gal- 

 lapagos.— Sowerby, 1833, Conch. Illust., No. 18, pi. 18, fig. 7.— Reeve, 1853, 

 Conch. Icon., vol, 8, Amphidesma, pi. 26. (as A. punctata.) 



Semele punctata (Sowerby), Maxwell Smith, 1944, Panamic Marine Shells, p. 62, fig. 

 809. 



The shell is ovate, sculptured wth coarse, concentric folds on the ven- 

 tral portion, finely radially striate. The umbonal surface is flat and coarsely 

 punctate as if due to weathering. Color is white, lightly maculated with 

 rose or purple. The figure is a photograph of the right valve of a specimen 

 from the Hanley collection in the British Museum (Natural History), 

 marked co-type. The specimen measures length 49.7 mm., height 39.1 mm. 



Range — Galapagos Islands, 



Semele tortuosa (C, B. Adams) Plate 64, figures 3-3b 



Amphidesma tortuosum C. B. Adams, 1852, Ann. Lyceum Nat. Hist. New York, vol. 

 5, pp. 515, 547, No. 490. 



Shell irregularly trigonal-ovate, compressed, the beaks high, submedian, 

 subequilateral, triangular above, rounded, subcircular below. The posterior 

 side is widely folded and twisted in each valve resulting in a median fold 

 bordered by two lateral depressed rays in the right valve and a correspond- 

 ing depressed, central furrow in the left valve. Surface sculptured principally 

 by waved, strong, concentric riblets thickly overrun by submicroscopic radial 

 threads. External color yellowish white, the interior also white or stained 

 with light yellow. The dorsal margin and hinge teeth may be white or 

 lilac-colored. 



Length 45.1 mm., height 40.9 mm., semidiameter 7.3 mm. right valve, 

 Puerto Callo, Ecuador. 



Length 62 mm., height 56.2 mm., semidiameter 12.4 mm, right valve, 

 Palo Seco, Panama Canal Zone, 



This is a rare species, as yet known only from a few loose valves. In 

 shape and sculpture, this species resembles S, decisa (Conrad) of California 

 but differs in detail. 



Range — Panama to Ecuador. Panama Canal Zone: Palo Seco. Ecuador: 

 Palmar; Puerto Callo; Manta; Sua. 



