60 AXEL A. OLSSON 



5. Average length about 15 mm. Rostrum is narrowly elliptical in shape. 



N. eburnea 

 cb. Concentric riblets raised and separated by wider and deeper interspaces, 

 cba. Rostral keel bordered in front or below by a deeply indented ray, thus 

 the posterior end of the shell may appear double-pointed. 



6. Shell subelongated, the concentric riblets coarse, separated by inter- 



spaces, wider than the riblets. 



N.dranga{V\.2,{\g.S) 



7. Shell shorter, higher and stubbier. Concentrics close. Anterior ray 

 lacking or weak. 



N. elenensis elenensis 



8. Anterior and posterior rays are both well developed. 



N. elenensis crispa 

 ebb. Posterior ray is absent or very weak. 



9. Concentric riblets relatively fine. Rostral keel rounded. 



N. callimene 



10. Concentric riblets stronger, the rostrum more sharply defined. 



N. acapidensis (PI. 2, figs. 8, 8a) 



11. Shell quite small, the concentric riblets strong. Anterior slope with an 

 indented ray or fold. 



A^. hindsii 



12. Shell small, concentric riblets strong. Rostrum is deeply concave bord- 

 ered by a coarsely noded keel. Anterior ray is also developed. 



N. excavata 



Xucnlana (Saccella) ornata (d'Orbigny) Plate 2, figures 3, 3a 



Leda ornata d'Orbigny, 1846, Voy. Amer. Merid., vol. S, p. 546, pi. 82, figs. 4, 5, 6; 



Hanley, 1860, in Sowerby, Thes. Conch., Nuculidae, p. 24, No. 41, pi. 228, figs. 



97, 98. 

 Nuculana ornata (d'Orbigny), Hertlein and Strong, 1940, Zoologica, vol. 2S, pt. 4, No. 



25, p. 405. 



Smaller than N. elenensis with a longer, more attenuated posterior 

 side terminating in a sharply pointed end. The anterior slope is crossed by 

 a wide, flat ray extending from the beak to the margin in front of which 

 the surface is sharply raised, its edge often more or less beaded by the 

 concentric sculpture. The sculpture is neat and regular, formed by concen- 

 trics of medium strength and regularly spaced over the whole surface. Pos- 

 terior or rostral keel strong, elevated, the enclosed rostral area wide, finely 

 sculptured with the continuation of the external concentrics of the disk but 

 more closely spaced. 



Fossil in the Pliocene of Ecuador. 



Range — Coasts of Peru and Ecuador. Peru: Bayovar, Bay of Sechura. 

 Paita. Ecuador: Manta. 



Nnculana (Saccella) acrita (Dall) Plate 2, figure 7 



Leda (Jupiteria) acrita Dall, 1908, Bull. Mus. Comp. Zoology, vol. 43, No. 6, pp. 374, 

 375 "Panama Bay". 



Leda laeviradius Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Philadelphia, vol. 84, p. 

 106, pi. 17, fig. 7 "Guaymas". 



Nuculana (Saccella) laeviradius (Pilsbry and Lowe), Hertlein and Strong, 1940, Zoo- 

 logica, vol. 25, pt. 4, pp. 396, 397, pi. 2, figs. 4, 7. 



Shell small (length 6 to 7 mm.), white or translucent, with a thin, pale 

 straw-colored periostracum, subequilateral, the anterior side swollen, the 

 posterior narrowly rostrate and acute at the end. Anterior dorsal margin 



