288 AXEL A. OLSSON 



Lamelliconcha paytensis (d'Orbigny) Plate 48, figures 6-6b 



Cytherea affinis Broderip, 1835, Proc. Zool. Soc. London, p. 45 Xipixapi. 

 Cytheraea affinis Broderip, Sowerby, 1851, Thes. Conch., vol. 2, p. 630, pi. 132, fig. 101. 

 Dione affinis (Broderip), Reeve, 1863, Conch. Icon., vol. 14, Dione, pi. 8, fig. 30. 

 Venus paytensis d'Orbigny, 1846, Voy. Amer. Merid., vol. 5, 3d pt. Mollusques, p. 565. 



(New name for affinis Broderip, not affinis Gmelin, 1789, not affinis Matheron, 



1842). 



Shell elongate, the posterior side is much longer than the anterior, the 

 posterior-dorsal and ventral margins approach each other so that the end 

 is narrowly rounded or bluntly pointed, often slightly emarginate along its 

 ventral margin. Surface compressed, sculptured with evenly spaced, narrow, 

 solid concentrics, uniformly developed over the whole disk. The strength 

 of these concentrics vary from relatively few and strong to more numerous 

 and small. Color of shell is often a pure white or variously marked with 

 wide or narrow rays of violet-red, the dorsal areas more deeply colored. 

 The posterior-dorsal margins flattened. 



Length 37.2 mm., height 25 mm., diameter 15.4 mm. Negritos, Peru. 



Length 37.8 mm., height 26.1 mm., diameter 17 mm. Punta Ostiones, 

 Esmeraldas. 



Common and more widely distributed than L. concinna from which it 

 is easily recognized by its longer shape; color usually white and is never 

 as strongly rayed or marked with violaceous red as L. concinna. The sculp- 

 ture is variable, the concentric riblets either strong and coarse or small and 

 fine. 



Range — Gulf of California ? southward to Peru. Panama: Puerto 

 Armuelles; Biicaro. Ecuador: Punta Ostiones, Esmeraldas; Sua; Manta; 

 Santa Elena. Peru: Tumbez; Punta Picos; Mancora; Negritos; Paita. 



Lamelliconcha tortuosa (Broderip) Plate 48, figures 5, 5a 



Cytherea tortuosa Broderip, 1835, Proc. Zool. Soc. London, p. 45 Panama and Xipixapi. 

 Cytheraea tortuosa Broderip, Sowerby, 1851, Thes. Conch., vol. 2, p. 630, pi. 132, fig. 103. 

 Dione tortuosa (Broderip), Reeve, 1863, Conch. Icon., vol. 14, Dione, pi. 12, fig. 61. 

 Pitar tortuosa (Broderip), Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Philadelphia, 

 vol. 84, p. 135. 



This species resembles /.. concimia in shape but is usually larger, 

 heavier, and the posterior end is somewhat sinuated or twisted, and the 

 normal color is white. The concentric lamellae are strong and may be 

 developed uniformly over the whole surface, or they may show varying 

 degrees of flexing below the posterior-umbonal angle as well as the intro- 

 duction of short lamella between them. The posterior umbonal slope is 

 well rounded. 



Length 40 mm., height 32 mm., diameter 21.9 mm. Puerto Chame, 

 Panama. 



This is a distinctive species, usually found along mud flats so often 

 present in front of a mangrove swamp where the waters may be partly 

 brackish. The color is typically white, and the concentric riblets have a 

 curious way of dividing as they cross the posterior half of the surface. 



Range^GwM of California to northern Peru. El Salvador: La Union, 

 Gulf of Fonseca (ANSP). Costa Rica: Puntarenas (ANSP). Panama: 



