62 AXEL A. OLSSON 



A well-marked species characterized by its strong sculpture and in 

 having minute crenulations along its inner ventral margin. 



Range — Lower California to Costa Rica. Mexico: Lower California; 

 Punta Penasco (Lowe); Guaymas (Pilsbry and Lowe). Costa Rica: Port 

 Parker (Hertlein and Strong). 



Ifuculana (Saecella) fastlgata Keen Plate 2, figures 2, 2a; Plate 3, figure 9 



Nucula gibbosa Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 198 "Tumbez". 



— Sowerby, 1833, Conch. Illust., Nuculae, p. 4, pi. IS, fig. 9. Not N. gibbosa of 



Fleming, 1828. 

 Leda gibbosa Hanley, 1860, in Sowerby, Thes. Conch., vol. 3, Nuculidae, p. 120, sp. 28, 



pi. 228, fig. 79. 

 Nuculana (Saccclla) gibbosa (Sowerby), Hertlein and Strong, 1940, Zoologica, vol. 25, 



pt. 4, pp. 395, 396, pi. 2, figs. 5, 8. 

 Nuculana (Saccella) fastigata Keen, 1958, Bull. Amer. Paleont, vol. 38, No. 172, p. 



240, pi. 31, figs. 1, 2. New name for A^. gibbosa Sowerb>/, 1833. 



Shell often quite large (max. length about 31 mm.), elongate-subovate, 

 convex and rather solid, white, often chalky, under an olive-brown periostra- 

 cum, the anterior side rather long with straight dorsal margin, the posterior 

 side narrowed and rostrated. Sculpture is formed by strong, narrowly rounded 

 concentric riblets, their intervals as wide and flat-bottomed; this sculpture 

 is nearly uniform over the whole surface. Anterior slope has a slightly de- 

 pressed ray which hardly affects the sculpture but may .sinuate the ventral 

 margin to a small degree. Anterior-dorsal area depressed, longitudinally 

 sculptured, the small lunule within smooth. Rostrum is quite large, ellipti- 

 cal, strongly sculptured, the rostral ridge low. Pallial sinus is large. 



Length 31 mm., height 17 mm., diameter 12.8 mm. 



Range — Mexico to Peru. Peru: Tumbez; Zorritos. 



Nacnlana (Saccella) ebarnea (Sowerby) Plate 2, figures 4, 4a; Plate 3, figure 10 



Nucula eburnea Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 198. — Sowerby, 1833, 



Conch. Illust., Nuculae, pp. 4, 6, pi. IS, fig. 10. 

 Leda eburnea Hanley, 1860, in Sowerby, Thes. Conch., vol. 3, Nuculidae, p. 124, No. 33, 



PI. 228, fig. 90. — Sowerby, 1871, Reeve, Conch. Icon., vol. 18, Laeda, pi. 5, fig. 29. 

 Nuculana (Saccella) eburnea (Sowerby), Hertlein and Strong, 1940, Zoologica, vol. 25, 



pt. 4, No. 25, p. 395, pi. 2, figs. 1, 2, 3. 



Shell of medium size (length up to about 16 mm.), about twice as long 

 as high, semi-elliptical, the umbones and beaks submedian, convex. Pos- 

 terior side narrowed, attenuate, the dorsal margin concave, the end pointed, 

 the anterior side narrowly rounded. Lunule distinct, elliptical, a trifle more 

 than half the length of the anterior side. Posterior-dorsal or rostral area 

 wide, as long as the posterior side, sculptured with straight, parallel lines 

 and defined by an outer angle. Surface is sculptured with evenly spaced, 

 incised lines forming concentric ribbons, uniformly developed over most of 

 the surface except for a narrow, smooth ray sometimes present just below 

 the posterior angle. 



The commonest species of Nuculana, easily recognized by its plain sculp- 

 ture of even, smooth concentrics, and well-defined lunule. 



Range — Gulf of Fonseca, El Salvador southward to northern Peru. 

 Panama: Bucaro. Canal Zone: Venado Beach; Colombia; Isla del Gallo. 

 Ecuador: Santa Elena; Punta Blanca; Galeras. Peru: Zorritos. 



